Philippines Air Force (PAF) personnel, deployed in the war-torn Marawi city, march during a Heroes' Welcome ceremony at the PAF headquarters in Pasay city, metro Manila, Philippines November 6, 2017. REUTERS/Romeo Ranoco

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, shows a tattoo with a portrait of his brother during a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, shows a tattoo with a portrait of his brother as he speaks during a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, shows a tattoo with a portrait of his brother as he as he speaks during a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, speaks during a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, shows a tattoo with a portrait of his brother as he arrives for a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Philippine Defence Secretary Delfin Lorenzana disembarks from the cockpit of a Cessna-208B Grand Caravan Intelligence, Surveillance and Reconnaissance (ISR) aircraft acquired by the Philippine government from the U.S. during a turn over ceremony at the Philippine Air Force (PAF) headquarters in Manila, Philippines July 27, 2017. REUTERS/Dondi Tawatao

U.S. Ambassador to the Philippines Sung Kim poses at the cockpit of a Cessna-208B Grand Caravan Intelligence, Surveillance and Reconnaissance (ISR) aircraft acquired by the Philippine government from the U.S. during a turn over ceremony at the Philippine Air Force (PAF) headquarters in Manila, Philippines July 27, 2017. REUTERS/Dondi Tawatao

U.S. Ambassador to the Philippines Sung Kim pours wine on a Cessna-208B Grand Caravan Intelligence, Surveillance and Reconnaissance (ISR) aircraft acquired by the Philippine government from the U.S. during a turn over ceremony at the Philippine Air Force (PAF) headquarters in Manila, Philippines July 27, 2017. REUTERS/Dondi Tawatao

U.S. Defense Secretary James Mattis (L) looks out at the tarmac as he boards a U.S. Air Force C-17 to depart Hamid Karzai International Airport after a daylong visit to Resolute Support headquarters in Kabul, Afghanistan April 24, 2017. REUTERS/Jonathan Ernst

FILE PHOTO: South Korean President Park Geun-hye salutes during a joint commissioning ceremony for 5,860 new officers from the Army, Navy, Air Force and Marines at the military headquarters in Gyeryong, south of Seoul March 6, 2014. REUTERS/Jung Yeon-je/Pool/File Photo TPX IMAGES OF THE DAY

Senior Counselor Steve Bannon boards Air Force One as he accompanies U.S. President Donald Trump to the U.S. Central Command (CENTCOM) and Special Operations Command (SOCOM) headquarters in Tampa at West Palm Beach International airport in West Palm Beach, Florida, U.S., February 6, 2017. REUTERS/Carlos Barria

Newly acquired from the U.S. C130 aircraft is seen parked at the tarmac at the Philippine Air Force headquarters in Villamor air base, Pasay city, metro Manila , Philippines October 24, 2016. REUTERS/Czar Dancel

U.S. Ambassador to the Philippines Philip Goldberg pours champagne on one of the C130 aircraft acquired from the U.S., at the Philippine Air Force (PAF) headquarters in Villamor air base, Pasay city, metro Manila, Philippines October 24, 2016. REUTERS/Czar Dancel

Philippine Defence Secretary Delfin Lorenzana pours champagne on one of the C130 aircraft acquired from the U.S., at the Philippine Air Force (PAF) headquarters in Villamor air base, Pasay city, metro Manila, Philippines October 24, 2016. REUTERS/Czar Dancel

Philippine Defense Secretary Delfin Lorenzana waves while inside on one of the C130 aircraft acquired from the U.S., at the Philippine Air Force (PAF) headquarters in Villamor air base, Pasay city, metro Manila, Philippines October 24, 2016. REUTERS/Czar Dancel

The Boeing logo is seen at their headquarters in Chicago, in this April 24, 2013 file photo. Boeing Co on April 27, 2016, reported a 9 percent drop in first-quarter profit, citing an after-tax charge from the KC-46 aerial refueling tanker it is developing for the U.S. Air Force. REUTERS/Jim Young/File Photo

Swiss Army Major General Urs Gerber (R) and Swedish Air Force Major General Mats Engman check a lamp inside a bunker at the Neutral Nations Supervisory Commissions (NNSC) headquarters near the truce village of Panmunjom, South Korea, March 30, 2016. REUTERS/Kim Hong-Ji

Swiss Army Major General Urs Gerber (R) and Swedish Air Force Major General Mats Engman walk along a barbed-wire fence at the Neutral Nations Supervisory Commissions (NNSC) headquarters near the truce village of Panmunjom, South Korea, March 30, 2016. REUTERS/Kim Hong-Ji

Swiss Army Major General Urs Gerber and Swedish Air Force Major General Mats Engman (L) walk on a bridge leading to Panmunjom, at the Neutral Nations Supervisory Commissions (NNSC) headquarters near the truce village of Panmunjom, South Korea, March 30, 2016. REUTERS/Kim Hong-Ji

Swiss Army Major General Urs Gerber (R) talks with Swedish Air Force Major General Mats Engman at the Neutral Nations Supervisory Commissions (NNSC) headquarters near the truce village of Panmunjom, South Korea, March 30, 2016. REUTERS/Kim Hong-Ji

NATO Supreme Allied Commander, U.S. Air Force General Philip Breedlove holds a news conference at the first ever gathering of the defense ministers of the Global Coalition Against ISIL/Daesh at NATO headquarters in Brussels, Belgium February 11, 2016. REUTERS/Virginia Mayo/Pool

Canadian Defense Minister Harjit Singh Sajjan (C) and NATO Supreme Allied Commander, U.S. Air Force General Philip Breedlove (R) attend a NATO defense ministers meeting at the Alliance's headquarters in Brussels February 10, 2016. REUTERS/Yves Herman

Canadian Defense Minister Harjit Singh Sajjan (L) and NATO Supreme Allied Commander, U.S. Air Force General Philip Breedlove (R) attend a NATO defense ministers meeting at the Alliance's headquarters in Brussels February 10, 2016. REUTERS/Yves Herman

NATO Supreme Allied Commander, U.S. Air Force General Philip Breedlove and German Defense Minister Ursula von der Leyen attend a NATO defense ministers meeting at the Alliance's headquarters in Brussels February 10, 2016. REUTERS/Yves Herman

New Bolivian military commanders, General Celier Aparicio, chief commander of the air forces, General Gina Reque Teran, general staff of the armed forces, General Juan Gonzalo Duran, commander-in-chief of the Bolivian Army, General Luis Arinez, chief commander of the army forces, and Vice-Admiral Jose Manuel Puente (L-R), chief commander of the naval forces, attend a news conference at the army headquarters building in La Paz, Bolivia, December 31, 2015. REUTERS/David Mercado

General Celier Aparicio, chief commander of Bolivia's air forces, talks with General Gina Reque Teran, general staff of the armed forces, while General Juan Gonzalo Duran (L-R), commander-in-chief of the Bolivian Army, looks on, after a news conference at the army headquarters building in La Paz, Bolivia, December 31, 2015. REUTERS/David Mercado

Journalists attend a briefing at the headquarters of Russia's defence ministry in Moscow, Russia, December 25, 2015. Russia's air force has made 5,240 sorties since it started the strikes in Syria on Sept. 30, including 189 sorties on Thursday alone, Russia's defence ministry told reporters on Friday. REUTERS/Maxim Zmeyev

NATO Supreme Allied Commander, U.S. Air Force General Philip Breedlove (C) stands with Chairman of the NATO Military Committee, Czech Army General Petr Pavel (L) and Supreme Allied Commander Transformation (SACT), French Air Force General General Denis Mercier (R) at the start of the NATO Ministerial Meeting on the South, Partnerships, and Defense Capacity at NATO Headquarters in Brussels, Belgium December 1, 2015. REUTERS/Jonathan Ernst

NATO Supreme Allied Commander, U.S. Air Force General Philip Breedlove (C) speaks with Chairman of the NATO Military Committee, Czech Army General Petr Pavel (L) and Supreme Allied Commander Transformation (SACT), French Air Force General General Denis Mercier (R) at the start of the NATO Ministerial Meeting on the South, Partnerships, and Defense Capacity at NATO Headquarters in Brussels, Belgium December 1, 2015. REUTERS/Jonathan Ernst TPX IMAGES OF THE DAY

U.S. Secretary of State John Kerry (L) greets NATO Supreme Allied Commander U.S. Air Force General Philip Breedlove (R) as they arrive for a NATO ministerial meeting on Resolute Support operations in Afghanistan, at NATO Headquarters in Brussels December 1, 2015. REUTERS/Jonathan Ernst

U.S. Secretary of State John Kerry (C) and NATO Secretary General Jens Stoltenberg (L) greet NATO Supreme Allied Commander U.S. Air Force General Philip Breedlove (R) as they arrive for a NATO ministerial meeting on Resolute Support operations in Afghanistan, at NATO Headquarters in Brussels December 1, 2015. REUTERS/Jonathan Ernst

Supporters of presidential candidate Daniel Scioli, of Argentina's ruling party, leave the party's headquarters in Buenos Aires, early October 26, 2015. Conservative opposition candidate Mauricio Macri took a surprise lead in Argentina's presidential election on Sunday, almost certainly forcing Scioli into a run-off vote next month, partial results showed. REUTERS/Marcos Brindicci

The campaign headquarters of Argentina's ruling party presidential candidate Daniel Scioli is pictured as supporters leave in Buenos Aires, early October 26, 2015. Conservative opposition candidate Mauricio Macri took a surprise lead in Argentina's presidential election on Sunday, almost certainly forcing Scioli into a run-off vote next month, partial results showed. The banner shows the pictures of Argentina's President Cristina Fernandez de Kirchner and candidate Daniel Scioli. REUTERS/Marcos Brindicci

The campaign headquarters of Argentina's ruling party presidential candidate Daniel Scioli is pictured as supporters leave in Buenos Aires, early October 26, 2015. Conservative opposition candidate Mauricio Macri took a surprise lead in Argentina's presidential election on Sunday, almost certainly forcing Scioli into a run-off vote next month, partial results showed. REUTERS/Marcos Brindicci

Houthi militants look at the headquarters of the offices of the education ministry's workers union, destroyed by Saudi-led air strikes, in Yemen's northwestern city of Amran August 19, 2015. A Saudi-led Arab coalition has been bombarding the Iranian-allied Houthi rebel movement - Yemen's dominant force - since late March in a bid to reinstate exiled President Abd-Rabbu Mansour Hadi, who has fled to Riyadh. REUTERS/Khaled Abdullah

Members of the Philippine Air Force push one of the two newly acquired AW-109E helicopters back to a hangar after a turnover ceremony at the Philippine Air Force (PAF) headquarters in Villamor Air Base in Pasay city, metro Manila August 17, 2015. The Philippines received 10 brand-new Bell-412EP and AW-109E helicopters from Canada and Italy to boost the air force's capabilities to provide close air support and air reconnaissance in counter-insurgency operations and transport for humanitarian assistance and disaster response, a Philippine Air Force official said. REUTERS/Romeo Ranoco

A military chaplain sprinkles holy water on one of the newly acquired Bell-412EP helicopters during a turnover ceremony at the Philippine Air Force (PAF) headquarters in Villamor Air Base in Pasay city, metro Manila August 17, 2015. The Philippines received 10 brand-new Bell-412EP and AW-109E helicopters from Canada and Italy to boost the air force's capabilities to provide close air support and air reconnaissance in counter-insurgency operations and transport for humanitarian assistance and disaster response, a Philippine Air Force official said. REUTERS/Romeo Ranoco

Members of the Philippine Air Force inspect one of the two AW-109E helicopters during a turnover ceremony at the Philippine Air Force (PAF) headquarters in Villamor Air Base in Pasay city, metro Manila August 17, 2015. The Philippines received 10 brand-new Bell-412EP and AW-109E helicopters from Canada and Italy to boost the air force's capabilities to provide close air support and air reconnaissance in counter-insurgency operations and transport for humanitarian assistance and disaster response, a Philippine Air Force official said. REUTERS/Romeo Ranoco

Members of the Philippine Air Force honor guard march in front of newly acquired Bell-412EP helicopters during a turnover ceremony at the Philippine Air Force (PAF) headquarters in Villamor Air Base in Pasay city, metro Manila August 17, 2015. The Philippines received 10 brand-new Bell-412EP and AW-109E helicopters from Canada and Italy to boost the air force's capabilities to provide close air support and air reconnaissance in counter-insurgency operations and transport for humanitarian assistance and disaster response, a Philippine Air Force official said. REUTERS/Romeo Ranoco

Defense Secretary Voltaire Gazmin pours champagne on one of the newly acquired Bell-412EP helicopters during a turnover ceremony at the Philippine Air Force (PAF) headquarters in Villamor Air Base in Pasay city, metro Manila August 17, 2015. The Philippines received 10 brand-new Bell-412EP and AW-109E helicopters from Canada and Italy to boost the air force's capabilities to provide close air support and air reconnaissance in counter-insurgency operations and transport for humanitarian assistance and disaster response, a Philippine Air Force official said. REUTERS/Romeo Ranoco

Lieutenant Commander Masato Maruyama of the Japanese Navy explains the flight plan of the P3-C Orion plane for a search and rescue training exercise, during a briefing at the Philippine Air Force headquarters in Puerto Princesa, Palawan, west Philippines June 23, 2015. The Japanese military patrol plane circled over disputed parts of the South China Sea on Tuesday at the start of an exercise with the Philippine military that has irked China. REUTERS/Romeo Ranoco

Lebanese and Arab students flash victory signs, shout slogans and carry signs during a protest against Saudi-led air strikes on Yemen, in front of the offices of the U.N. headquarters in Beirut April 1, 2015. Saudi Arabia is leading a coalition of Arab states in an air campaign against the Shi'ite Houthis, who emerged as the most powerful force in the Arabian Peninsula's poorest country when they seized Yemen's capital last year. REUTERS/Mohamed Azakir

Arab students shout slogans, carry banners and a Yemeni national flag during a protest against Saudi-led air strikes on Yemen, in front of the offices of the U.N. headquarters in Beirut April 1, 2015. Saudi Arabia is leading a coalition of Arab states in an air campaign against the Shi'ite Houthis, who emerged as the most powerful force in the Arabian Peninsula's poorest country when they seized Yemen's capital last year. REUTERS/Mohamed Azakir

Lebanese and Arab students carry signs and Yemeni national flags during a protest against Saudi-led air strikes on Yemen, in front of the offices of the U.N. headquarters in Beirut April 1, 2015. Saudi Arabia is leading a coalition of Arab states in an air campaign against the Shi'ite Houthis, who emerged as the most powerful force in the Arabian Peninsula's poorest country when they seized Yemen's capital last year. The signs read, "They export the violence, to stay governors" (L) and "Shame on you officials" (R). REUTERS/Mohamed Azakir

Arab students shout slogans, and carry banners and a Yemeni national flag during a protest against Saudi-led air strikes on Yemen, in front of the offices of the U.N. headquarters in Beirut April 1, 2015. Saudi Arabia is leading a coalition of Arab states in an air campaign against the Shi'ite Houthis, who emerged as the most powerful force in the Arabian Peninsula's poorest country when they seized Yemen's capital last year. REUTERS/Mohamed Azakir

New South Korean military officers arrive at a joint commissioning ceremony for 6,478 new officers from the Army, Navy, Air Force and Marines at the military headquarters in Gyeryong March 12, 2015. REUTERS/Kim Hong-Ji (SOUTH KOREA - Tags: MILITARY SOCIETY)

New South Korean military officers attend a joint commissioning ceremony for 6,478 new officers from the Army, Navy, Air Force and Marines at the military headquarters in Gyeryong March 12, 2015. REUTERS/Kim Hong-Ji (SOUTH KOREA - Tags: MILITARY SOCIETY)

A new South Korean military officer adjusts his fellow officer's cap during a joint commissioning ceremony for 6,478 new officers from the Army, Navy, Air Force and Marines at the military headquarters in Gyeryong March 12, 2015. REUTERS/Kim Hong-Ji (SOUTH KOREA - Tags: MILITARY SOCIETY)

New South Korean military officers salute the national flag during a joint commissioning ceremony for 6,478 new officers from the Army, Navy, Air Force and Marines at the military headquarters in Gyeryong March 12, 2015. REUTERS/Kim Hong-Ji (SOUTH KOREA - Tags: MILITARY SOCIETY)

New South Korean military officers cheer during a joint commissioning ceremony for 6,478 new officers from the Army, Navy, Air Force and Marines at the military headquarters in Gyeryong March 12, 2015. REUTERS/Kim Hong-Ji (SOUTH KOREA - Tags: MILITARY SOCIETY)

A new South Korean military officer runs into an echelon as they attend a joint commissioning ceremony for 6,478 new officers from the Army, Navy, Air Force and Marines at the military headquarters in Gyeryong March 12, 2015. REUTERS/Kim Hong-Ji (SOUTH KOREA - Tags: MILITARY SOCIETY TPX IMAGES OF THE DAY)

South Korean honor guards perform before a joint commissioning ceremony for 6,478 new officers from the Army, Navy, Air Force and Marines at the military headquarters in Gyeryong March 12, 2015. REUTERS/Kim Hong-Ji (SOUTH KOREA - Tags: MILITARY SOCIETY)

A plane belonging to the Jordanian Royal Air Force flies over the headquarters of the family clan of pilot Muath al-Kasaesbeh in the city of Karak February 4, 2015. Jordan hanged two Iraqi jihadists on Wednesday including a female militant in response to an Islamic State video showing captured Jordanian pilot Muath al-Kasaesbeh being burnt alive by the hardline group. Islamic State had demanded the release of the woman, Sajida al-Rishawi, in exchange for a Japanese hostage who it later beheaded. Sentenced to death in 2005 for her a role in a suicide bomb attack in Amman, Rishawi was executed at dawn, a security source and state television said. Jordan also executed a senior al Qaeda prisoner, Ziyad Karboli, an Iraqi man who was sentenced to death in 2008. REUTERS/Muhammad Hamed (JORDAN - Tags: POLITICS CRIME LAW CIVIL UNREST CONFLICT)

Planes belonging to the Jordanian Royal Air Force fly over the headquarters of the family clan of pilot Muath al-Kasaesbeh in the city of Karak February 4, 2015. Jordan hanged two Iraqi jihadists on Wednesday including a female militant in response to an Islamic State video showing captured Jordanian pilot Muath al-Kasaesbeh being burnt alive by the hardline group. Islamic State had demanded the release of the woman, Sajida al-Rishawi, in exchange for a Japanese hostage who it later beheaded. Sentenced to death in 2005 for her a role in a suicide bomb attack in Amman, Rishawi was executed at dawn, a security source and state television said. Jordan also executed a senior al Qaeda prisoner, Ziyad Karboli, an Iraqi man who was sentenced to death in 2008. REUTERS/Muhammad Hamed (JORDAN - Tags: CIVIL UNREST CRIME LAW POLITICS CONFLICT)

Planes belonging to the Jordanian Royal Air Force fly over the headquarters of the family clan of pilot Muath al-Kasaesbeh in the city of Karak February 4, 2015. Jordan hanged two Iraqi jihadists on Wednesday including a female militant in response to an Islamic State video showing captured Jordanian pilot Muath al-Kasaesbeh being burnt alive by the hardline group. Islamic State had demanded the release of the woman, Sajida al-Rishawi, in exchange for a Japanese hostage who it later beheaded. Sentenced to death in 2005 for her a role in a suicide bomb attack in Amman, Rishawi was executed at dawn, a security source and state television said. Jordan also executed a senior al Qaeda prisoner, Ziyad Karboli, an Iraqi man who was sentenced to death in 2008. REUTERS/Muhammad Hamed (JORDAN - Tags: POLITICS CRIME LAW CIVIL UNREST CONFLICT)

Relatives of Islamic State captive Jordanian pilot Muath al-Kasaesbeh place a poster of him in front of their new gathering headquarters in Amman January 30, 2015. Jordan's army said on Friday state agencies were working to get information on the air force pilot held by Islamic State militants, after a deadline passed for a proposed prisoner swap, but offered no new word on his fate. The pilot was captured after his jet crashed in northeastern Syria in December during a bombing mission against Islamic State. REUTERS/Muhammad Hamed (JORDAN - Tags: POLITICS CIVIL UNREST CRIME LAW)

U.S. soldiers from the 3rd Cavalry Regiment practice with an Air Force Joint Terminal Attack Controller (JTAC) (R) while on an advising mission at the Afghan National Army headquarters for the 203rd Corps in the Paktia province of Afghanistan December 21, 2014. REUTERS/Lucas Jackson (AFGHANISTAN - Tags: CIVIL UNREST POLITICS MILITARY)

German Defence Minister Ursula von der Leyen (C) travels on a German Air Force helicopter to the International Security Assistance Force (ISAF) headquarters in Kabul, December 14, 2014. REUTERS/John MacDougall/Pool (AFGHANISTAN - Tags: POLITICS MILITARY)

German Defence Minister Ursula von der Leyen disembarks a German Air Force helicopter at the International Security Assistance Force (ISAF) headquarters in Kabul, December 14, 2014. REUTERS/John MacDougall/Pool (AFGHANISTAN - Tags: POLITICS MILITARY)