Departing passengers wait to board their flight at the departure gates at Malta International Airport in Luqa, Malta August 2, 2017. REUTERS/Darrin Zammit Lupi 

Signage pointing to the departure gates and VIP lounge is seen in a Duty Free store at Malta International Airport in Luqa, Malta August 2, 2017. REUTERS/Darrin Zammit Lupi 

Passengers go through a security check before walking to departure gates at the Sydney Airport Domestic terminal in Australia, July 30, 2017. REUTERS/David Gray 

Passengers are reflected in the glass of the departure hall as they leave from a Turkish Airlines aircraft at the airport in Konya, Turkey, October 20, 2016. REUTERS/Murad Sezer 

JetBlue Airways aircrafts are pictured at departure gates at John F. Kennedy International Airport in New York June 15, 2013. REUTERS/Fred Prouser/File Photo 

Members of the U.S. Army monitor the departures area at John F. Kennedy international Airport in the Queens borough of New York, U.S., June 29, 2016. REUTERS/Andrew Kelly

Members of the U.S. Army monitor the departures area at John F. Kennedy international Airport in the Queens borough of New York, U.S., June 29, 2016. REUTERS/Andrew Kelly

A U.S. Army Specialist monitors the security line at John F. Kennedy international Airport in the Queens borough of New York, U.S., June 29, 2016. REUTERS/Andrew Kelly

A U.S. Army Specialist monitors the security line at John F. Kennedy international Airport in the Queens borough of New York, U.S., June 29, 2016. REUTERS/Andrew Kelly

A Port Authority Police Officer monitors the departures area at LaGuardia Airport in the lead up to the holiday weekend in the Queens borough of New York, U.S., June 29, 2016. REUTERS/Andrew Kelly 

People walk past closed departure gates, under a faulty flight information display screen, during a partial power failure after heavy rains caused flooding at Taoyuan International Airport, Taiwan June 2, 2016. REUTERS/Tyrone Siu TPX IMAGES OF THE DAY

People walk past closed departure gates, under a faulty flight information display screen, during a partial power failure after heavy rains caused flooding at Taoyuan International Airport, Taiwan June 2, 2016. REUTERS/Tyrone Siu

Singapore Airlines flight attendants walk to the departure gate at Changi Airport in Singapore May 11, 2016. REUTERS/Edgar Su

The ADP (Groupe Aeroports de Paris) new logo for travelers, "Paris Aeroport", is seen at a new departure gate in Orly airport, near Paris, France, April 14, 2016. REUTERS/Benoit Tessier/File Photo GLOBAL BUSINESS WEEK AHEAD PACKAGE - SEARCH 'BUSINESS WEEK AHEAD MAY 2' FOR ALL IMAGES 

The ADP (Groupe Aeroports de Paris) new logo for travelers, "Paris Aeroport", is seen at a new departure gate in Orly airport, near Paris, France, April 14, 2016. REUTERS/Benoit Tessier 

The ADP (Groupe Aeroports de Paris) new logo for travelers, "Paris Aeroport", is seen at a new departure gate in Orly airport, near Paris, France, April 14, 2016. REUTERS/Benoit Tessier 

The ADP (Groupe Aeroports de Paris) new logo for travelers, "Paris Aeroport", is seen at a new departure gate in Orly airport, near Paris, France, April 14, 2016. REUTERS/Benoit Tessier 

A general view shows a new departure gate at Orly airport, near Paris, France, April 14, 2016. MEPs voted on Thursday on the EU Passenger Name Record (PNR) Directive, which would oblige airlines to hand EU countries their passengers' data in order to help the authorities to fight terrorism and serious crimes.REUTERS/Benoit Tessier 

U.S. President Barack Obama and his daughter Malia walk from Marine One to board Air Force One upon their departure from O'Hare Airport in Chicago April 7, 2016. REUTERS/Kevin Lamarque TPX IMAGES OF THE DAY

Check-in and departure gates signs are seen at the terminal at Fiumicino's International airport near Rome, Italy, March 23, 2016. REUTERS/Stefano Rellandini 

A sign of the departure gate is seen at the terminal at Fiumicino's International airport near Rome, Italy, March 23, 2016. REUTERS/Stefano Rellandini 

Check-in and departure gates signs are seen at the terminal at Fiumicino's International airport near Rome, Italy, March 23, 2016. REUTERS/Stefano Rellandini 

A sign of the departure gate is seen at the terminal at Fiumicino's International airport near Rome, Italy, March 23, 2016. REUTERS/Stefano Rellandini 

A banner is seen during an information campaign on Zika virus by the Chilean Health Ministry at the departures area of Santiago's international airport, Chile, January 28, 2016. The banner reads: "Zika virus, know before your trip. Use repellents on exposed areas. Use air conditioner or mosquito netting." REUTERS/Ivan Alvarado 

Chile's Health Minister Carmen Castillo (C) talks to the media during an information campaign on Zika virus by the Chilean Health Ministry at the departures area of Santiago's international airport, Chile January 28, 2016. The banner reads: "Zika virus, know before your trip". REUTERS/Ivan Alvarado 

Chile's Health Minister Carmen Castillo holds a flyer that reads "Zika virus recommendations" during an information campaign by the Health Ministry at the departures area of Santiago's international airport, Chile January 28, 2016. REUTERS/Ivan Alvarado 

A man reads a zika virus flyer from an information campaign by the Chilean Health Ministry at the departures area of Santiago's international airport, Chile January 28, 2016. REUTERS/Ivan Alvarado TPX IMAGES OF THE DAY

Women read zika virus flyers from an information campaign by the Chilean Health Ministry at the departures area of Santiago's international airport, Chile January 28, 2016. The flyers read: "Zika virus recommendations." REUTERS/Ivan Alvarado

A woman holds a zika virus flyer from an information campaign by the Chilean Health Ministry at the departures area of Santiago's international airport, Chile January 28, 2016. The flyer reads: "Zika virus recommendations." REUTERS/Ivan Alvarado

A woman holds a zika virus flyer from an information campaign by the Chilean Health Ministry hugs another at the departures area of Santiago's international airport, Chile January 28, 2016. REUTERS/Ivan Alvarado

Miss World Canada Anastasia Lin poses for photo at the departure hall of Hong Kong Airport in Hong Kong, China November 26, 2015. Canada's China-born Miss World contestant Lin was stopped in Hong Kong on Thursday and denied permission to board a flight to the beauty pageant finals in China, a move she said was punishment for speaking out against human rights abuses in the country. REUTERS/Tyrone Siu TPX IMAGES OF THE DAY

Members of the police airport security with a sniffing dog stand guard in front of the departure area of the international airport in Pasay city, metro Manila August 19, 2015. The PNP and other agencies concerned, are stepping up security in the airport, after a recent bomb blast in Bangkok, Thailand, which killed 22 people, almost half of whom are foreigners, and wounded more than 120. REUTERS/Romeo Ranoco 

Members of the Philippine National Police (PNP) aviation security with a sniffing dog inspect the baggage of passengers before they enter the departure area of the international airport in Pasay city, metro Manila August 19, 2015. The PNP and other agencies concerned are on alert after the recent Thailand blast that killed 22, almost half of which are foreigners, and wounded more than 120. REUTERS/Romeo Ranoco 

Members of the Philippine National Police (PNP) aviation security with a sniffing dog stand guard in front of the departure area of the international airport in Pasay city, metro Manila August 19, 2015. The PNP and other agencies concerned are on alert after the recent Thailand blast that killed 22, almost half of which are foreigners, and wounded more than 120. REUTERS/Romeo Ranoco 

Departure and arrival sections are pictured at the Jaisalmer Airport in desert state of Rajasthan, India, August 13, 2015. Two-and-a-half years after the completion of a new $17 million terminal building, the airport in Jaisalmer, a small and remote desert city in India's western Rajasthan state, stands empty. Not a single passenger has passed through the gates of an airport big enough to handle more than 300,000 travellers a year, with parking bays for three 180-seater narrow-body jets. India has spent more than $50 million since 2009 on eight airports that do not receive scheduled flights - white elephants that are a reminder of the pitfalls for Prime Minister Narendra Modi as he bets on an infrastructure drive to fuel growth. Picture taken August 13, 2015. REUTERS/Anindito Mukherjee 

Departure and arrival sections are pictured at the Jaisalmer Airport in desert state of Rajasthan, India, August 13, 2015. Two-and-a-half years after the completion of a new $17 million terminal building, the airport in Jaisalmer, a small and remote desert city in India's western Rajasthan state, stands empty. Not a single passenger has passed through the gates of an airport big enough to handle more than 300,000 travellers a year, with parking bays for three 180-seater narrow-body jets. India has spent more than $50 million since 2009 on eight airports that do not receive scheduled flights - white elephants that are a reminder of the pitfalls for Prime Minister Narendra Modi as he bets on an infrastructure drive to fuel growth. Picture taken August 13, 2015. REUTERS/Anindito Mukherjee 

Tourists stand in front of the Departure gate of Tribhuvan International Airport as they wait for their flight after an earthquake in Kathmandu, Nepal April 28, 2015. REUTERS/Navesh Chitrakar 

People gather by a departure gate at Sanaa International Airport, where foreigners are being evacuated from Yemen April 6, 2015. Foreign nationals were on their way out of Yemen on Monday as 12 days of strikes by a Saudi-led coalition have failed to halt the advance of the Iran-allied Houthis and triggered a growing humanitarian crisis for residents in central districts now cut off from the mainland. REUTERS/Khaled Abdullah 

People gather by a departure gate at Sanaa International Airport, where foreigners are being evacuated from Yemen April 6, 2015. Foreign nationals were on their way out of Yemen on Monday (April 6) as 12 days of strikes by a Saudi-led coalition have failed to halt the advance of the Iran-allied Houthis and triggered a growing humanitarian crisis for residents in central districts now cut off from the mainland. REUTERS/Khaled Abdullah 

A worker guides a woman to a departure gate at Sanaa International Airport, where foreigners are being evacuated from Yemen April 6, 2015. Foreign nationals were on their way out of Yemen on Monday as 12 days of strikes by a Saudi-led coalition have failed to halt the advance of the Iran-allied Houthis and triggered a growing humanitarian crisis for residents in central districts now cut off from the mainland. REUTERS/Khaled Abdullah 

A boy looks as he stands by a departure gate at Sanaa International Airport where foreigners are being evacuated from Yemen April 6, 2015. Foreign nationals were on their way out of Yemen on Monday as 12 days of strikes by a Saudi-led coalition have failed to halt the advance of the Iran-allied Houthis and triggered a growing humanitarian crisis for residents in central districts now cut off from the mainland. REUTERS/Khaled Abdullah 

A woman gestures as she queues by a departure gate at Sanaa International Airport, where foreigners are being evacuated from Yemen April 6, 2015. Foreign nationals were on their way out of Yemen on Monday as 12 days of strikes by a Saudi-led coalition have failed to halt the advance of the Iran-allied Houthis and triggered a growing humanitarian crisis for residents in central districts now cut off from the mainland. REUTERS/Khaled Abdullah 

A stranded passenger sits near the departure gate along with his luggage at Tribhuvan International Airport in Kathmandu March 6, 2015. According to local media, the Tribhuvan International Airport has been closed since Wednesday morning after a Turkish Airlines plane skidded off the runway during landing. REUTERS/Navesh Chitrakar (NEPAL - Tags: TRANSPORT) 

A closed departure gate is seen at the airport in Lodz October 10, 2014. Picture taken October 10, 2014. To match Special Report POLAND-AIRPORTS/ REUTERS/Kacper Pempel (POLAND - Tags: TRANSPORT BUSINESS TRAVEL) 

A closed Lufthansa departure gate is pictured in a terminal at Fraport airport in Frankfurt September 29, 2014. Lufthansa pilots will strike on Tuesday after talks over an early retirement scheme broke down again, taking out long-haul flights from Frankfurt between 0600 and 2100 GMT. The Vereinigung Cockpit (VC) trade union said on Monday that Airbus A380, A330 and A340 and Boeing B747 aircraft would not fly from Frankfurt. A spokesman for the union estimated that 70 to 80 flights would be affected. Lufthansa had no immediate comment. REUTERS/Kai Pfaffenbach (GERMANY - Tags: TRANSPORT BUSINESS EMPLOYMENT) 

A closed Lufthansa departure gate is pictured in a terminal at Fraport airport in Frankfurt September 29, 2014. Lufthansa pilots will strike on Tuesday after talks over an early retirement scheme broke down again, taking out long-haul flights from Frankfurt between 0600 and 2100 GMT. The Vereinigung Cockpit (VC) trade union said on Monday that Airbus A380, A330 and A340 and Boeing B747 aircraft would not fly from Frankfurt. A spokesman for the union estimated that 70 to 80 flights would be affected. Lufthansa had no immediate comment. REUTERS/Kai Pfaffenbach (GERMANY - Tags: TRANSPORT BUSINESS EMPLOYMENT) 

A general view of the new Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT) 

A general view inside the new Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT) 

Passengers wait for departure at Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT) 

A general view of the new Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT) 

A general view of the new Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT) 

A passenger stands at Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT) 

A general view of the new Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: TRANSPORT SPORT SOCCER WORLD CUP) 

Passengers walk past the departure entrance of Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT) 

Brazilian President Dilma Rousseff gestures as she attends the inauguration of Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT POLITICS) 

Brazilian President Dilma Rousseff speaks as she attends the inauguration of Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT POLITICS) 

Brazilian President Dilma Rousseff speaks as she attends the inauguration of Terminal 3 at Guarulhos International airport in Sao Paulo May 20, 2014. The new terminal includes 20 departure gates, a runway with a capacity for 34 aircraft, and is expected to receive 12 million passengers each year. REUTERS/Paulo Whitaker (BRAZIL - Tags: SPORT SOCCER WORLD CUP TRANSPORT POLITICS) 

British tourists queue at the departure gate as they are being evacuated at Moi International Airport in the Kenyan coastal city of Mombasa, May 15, 2014. Kenya rebuked Britain, the United States, Australia and France on Thursday for issuing warnings about travel to the east African country, while hoteliers said at least 400 tourists had checked out of hotels along the Indian Ocean coast. REUTERS/Joseph Okanga (KENYA - Tags: TRAVEL CIVIL UNREST) 

Snow removal equipment is used near the departure and arrival gates at Baltimore Washington International Thurgood Marshall Airport outside Baltimore, Maryland February 13, 2014. A deadly and intensifying winter storm packing heavy snow, sleet and rain pelted a huge swath of the U.S. East Coast on Thursday, grounding flights and shuttering schools and government offices. REUTERS/Gary Cameron (UNITED STATES - Tags: ENVIRONMENT TRANSPORT) 

People wait at a gate that reads, "Philippine Airlines departure", in the devastated arrival area of the Tacloban airport building November 17, 2013.The Philippines is facing up to an enormous rebuilding task from Typhoon Haiyan, which killed at least 3,974 people and left 1,186 missing, with many isolated communities yet to receive significant aid despite a massive international relief effort. REUTERS/Wolfgang Rattay (PHILIPPINES - Tags: DISASTER ENVIRONMENT TRANSPORT)