A Boeing F/A-18 takes off to perform during the Farnborough International Airshow in Farnborough, Britain, 12 July 2016. The Farnborough International Air Show runs from 11-17 July. (Photo by Hannah Mckay/EPA)

A F-16 fighter jet from The Thai Royal Air Force performs during a media demonstration at the Korat Royal Thai Air Force Base, Nakhon Ratchasima province, Thailand, November 24, 2015. Thailand's military held an air show with China on Tuesday ahead of joint manoeuvres in a sign of warming ties, but Thailand said it was not distancing itself from the United States which downgraded the military relationship following a 2014 coup. (Photo by Athit Perawongmetha/Reuters)

A paddle boarder watches a hot air balloon flying low over Lake Burley Griffin on the 30th anniversary of Canberra's Balloon Spectacular festival in Australia's capital, March 14, 2016. (Photo by Lukas Coch/Reuters/AAP)

Crew members work to secure a hot air balloon after landing during the 2015 Albuquerque International Balloon Fiesta in Albuquerque, New Mexico, October 4, 2015. (Photo by Lucas Jackson/Reuters)

A view of balloon depicting an Alebrije, is seen at the 14th Solar Balloon Festival in Envidago December 31, 2014. According to the festival organizers, the Alebrije balloon will be largest replica of an Alebrije. This year features a theme on Mexican history and culture, organizers added. (Photo by Fredy Builes/Reuters)

Wizz Air's Airbus A-321 flying along the Danibe river during an air show in Budapest, Hungary, May 1, 2016. (Photo by Laszlo Balogh/Reuters)

Pedestrians cover their face as they walk along the dusty road in Kathmandu, Nepal February 27, 2017. Nepal has forced 2,500 old vehicles off roads in its capital city of Kathmandu, part of a fight against alarming air pollution levels that have hit nine times World Health Organisation (WHO) limits. Air pollution has been a chronic problem in rapidly growing Kathmandu, which sits in a Himalayan valley and is home to more than 3mn people. (Photo by Navesh Chitrakar/Reuters)

An Aerial view Admiralty Arch at the top of The Mall on July 26, 2011 in London, England. (Photo by Tom Shaw/Getty Images)