A U.S. Marine Osprey sends up a big wash of rain as as it lands near the Bavarian town of Kruen, Germany, June 8, 2015. The Ospreys provided transport to Air Force One in Munich for members of U.S. President Barack Obama's staff, Secret Service, White House Press Corps and other personnel at the conclusion of the G7 Summit. REUTERS/Kevin Lamarque 

Reporters are whipped by blowing snow as U.S. President Barack Obama departs via the Marine One helicopter from the White House in Washington March 6, 2015. Obama is making a day trip to South Carolina. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS MEDIA TPX IMAGES OF THE DAY) 

Nepal Army personnel take cover as an Indian Airforce helicopter evacuating injured residents takes off following Saturday's earthquake in Sindhupalchowk, Nepal, April 28, 2015. REUTERS/Danish Siddiqui 

A U.S. soldier from the 3rd Cavalry Regiment shields himself from the rotor wash of a UH-60 Blackhawk helicopter after being dropped off for a mission with the Afghan police near Jalalabad in the Nangarhar province of Afghanistan December 20, 2014. REUTERS/Lucas Jackson (AFGHANISTAN - Tags: TRANSPORT CIVIL UNREST MILITARY POLITICS TPX IMAGES OF THE DAY) 

An Israeli naval personnel directs an Israeli helicopter as it lands during a drill aboard a corvette military vessel on international waters May 13, 2015. U.S., Greek and Israeli navies took part in "Noble Dina", a two-week long trilateral naval exercise focusing on maritime cooperation between the participating nations. Picture taken May 13, 2015. REUTERS/Amir Cohen 

A French Gendarmerie rescue helicopter drops rescue workers next to the debris of the Airbus A320 at the site of the crash, near Seyne-les-Alpes, French Alps March 29, 2015. The co-pilot suspected of deliberately crashing a passenger plane in the French Alps told his girlfriend he was in psychiatric treatment, and that he was planning a spectacular gesture that everyone would remember, the German daily Bild reported on Saturday. REUTERS/Gonzalo Fuentes

Members of the press, including NBC's Evan Dixon (R), face the blowing snow caused by Marine One as it lands on the South Lawn before picking up U.S. President Barack Obama at the White House in Washington, January 7, 2015. Obama is departing for a two-day trip to Michigan and Arizona. REUTERS/Larry Downing (UNITED STATES - Tags: POLITICS ENVIRONMENT) 

A helicopter draws water from a lake as smoke rises from the King Fire in Pollock Pines, California September 17, 2014. Fire crews in California's rugged Sierra Nevada battled to gain the upper hand on Wednesday against a blaze that threatened 1,600 homes and has displaced 2,100 residents as flames roared for a fifth day through dry timber and brush west of Lake Tahoe. REUTERS/Noah Berger (UNITED STATES - Tags: TRANSPORT DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) 

Paratroopers from Chosen Company of the 3rd Battalion (Airborne), 509th Infantry board a waiting CH-47 Chinook helicopter as they begin a helicopter assault mission at Combat Outpost Herrera in Afghanistan's Paktiya Province July 15, 2012. Picture taken July 15. REUTERS/Lucas Jackson (AFGHANISTAN - Tags: CIVIL UNREST MILITARY TPX IMAGES OF THE DAY) FOR BEST QUALITY IMAGE ALSO SEE: GF2EA4T19JV01 

A U.S. Marine watches as an Osprey carrying U.S. Defense Secretary Leon Panetta arrives at Forward Operating Base Shukvani, Afghanistan March 14, 2012. Panetta told troops in Afghanistan on Wednesday that the massacre of 16 Afghan civilians by an American soldier should not deter them from their mission to secure the country ahead of a 2014 NATO withdrawal deadline. REUTERS/Scott Olson/Pool (AFGHANISTAN - Tags: POLITICS MILITARY TPX IMAGES OF THE DAY) 

A U.S. army medic from 2-35 Infantry Battalion protects an Afghan national army soldier injured by gun fire and rocket propelled grenades fired by the Taliban as a Medevac helicopter lands at a forward firebase fortress in Kunar province, Afghanistan, July 11, 2011. REUTERS/Baz Ratner (AFGHANISTAN - Tags: CONFLICT MILITARY TRANSPORT) 

A helicopter flies next to Spanish soldiers of the Marine infantry brigade who are holding their weapons as they simulate an assault, as Spanish aircraft carrier Principe de Asturias sails on La Malagueta beach, during a military operational exhibition on the eve of celebrations to mark Spanish Armed Forces Day in Malaga, southern Spain, May 28, 2011. REUTERS/Jon Nazca (SPAIN - Tags: ANNIVERSARY MILITARY) 

A Pakistani soldier crouches as a Pakistani Army Mi-17 helicopter takes off on top of Kund mountain near Kotkai village in South Waziristan October 29, 2009. The Pakistani army is zeroing in on two major Taliban sanctuaries in their South Waziristan bastion as government forces pressed ahead with their offensive in the lawless tribal region on the Afghan border. REUTERS/Nicolas Asfouri/Agency/Pool (PAKISTAN POLITICS MILITARY CONFLICT) 

Residents are rescued by helicopter from the floodwaters of Hurricane Katrina in New Orleans September 1, 2005. Chaos and lawlessness hampered the evacuation of New Orleans on Thursday and a U.S. senator said thousands may have died in Louisiana after Hurricane Katrina devastated the U.S. Gulf Coast. In New Orleans, shell-shocked officials tried to regain control of the historic jazz city reduced to a swampy ruin by Monday's storm. Bodies floated in the flooded city and authorities still could only guess how many people had died. REUTERS/David J. Phillip/Pool LA 

Acehnese men struggle with the down draft of a U.S. military helicopter as it lands on the west coast of tsunami-hit province of Aceh. Acehnese men struggle with the down draft of a U.S. military helicopter as it lands to deliver food aid at a village on the west coast of tsunami-hit province of Aceh on January 13, 2005. REUTERS/Supri