In this September 25, 2016, file photo, a remote-controlled F-16 fighter jet lands in front of an Air Koryo commercial airplane at the Kalma Airport after a flight demonstration in Wonsan, North Korea. With U.S. President Donald Trump and North Korean leader Kim Jong Un descending on Hanoi for their second summit, there has been a persistent suggestion that Kim will look around at the relative prosperity of his Vietnamese hosts – who are certainly no strangers to U.S. hostility – and think that he, too, should open up his country to more foreign investment and trade. (Photo by Wong Maye-E/AP Photo)





A handout picture made available by Solar Impulse shows a selfie picture by Swiss pioneer Bertrand Piccard onboard Solar Impulse2 prior to landing in Seville in Spain on 23 June 2016, finishing a 70 hours flight over the Atlantic ocean. (Photo by EPA/EFE/Solar Impulse Handout)





“Turkish Stars”, F-5 fighter airplanes, the aerobatic team of the Turkish Air Force, fly in formation over Istanbul's new airport, during the Teknofest aviation, space and technology fair, Sunday, September 23, 2018. The fair took place between Sept. 20-23 at Istanbul's new international airport, still under construction. (Photo by Emrah Gurel/AP Photo)





In this Monday, July 23, 2018 photo, heat ripples blur the downtown skyline as a jet lands in Phoenix, Ariz., as temperatures exceed 100 degrees in the morning hours. Already devilishly hot for being in the Sonoran desert, Arizona’s largest city is also an “urban heat island”, a phenomenon that pushes up temperatures in areas covered in heat-retaining asphalt and concrete. Phoenix officials say they are tackling urban warming, monitoring downtown temperatures, planting thousands of trees and capturing rainwater to cool off public spaces. (Photo by Matt York/AP Photo)





This May 29, 2018 photo provided by Virgin Galactic shows the VSS Unity craft during a supersonic flight test. The spaceship isn’t launched from the ground but is carried beneath a special aircraft to an altitude around 50,000 feet (15,240 meters). There, it’s released before igniting its rocket engine and climbing. (Photo by Virgin Galactic via AP Photo)





A plane carrying Britain's Prince Harry takes off after his official visit in Georgetown, Guyana December 4, 2016. (Photo by Carlo Allegri/Reuters)





A specially painted, co-branded Alaska Airlines and Virgin America 737-900ER aircraft, painted in shimmering red, purple and blue and featuring the slogan “More to love”, lands at San Francisco International Airport, California, U.S., December 14, 2016. The newly painted aircraft is part of the merger celebration of Alaska Airlines and Virgin America. (Photo by Courtesy Bob Riha, Jr./Reuters/Alaska Airlines)





Two airliners pass in the sky above Malta as the drama of a hijacked Libyan Afriqiyah Airways Airbus A320 is played out on the runway beneath at Malta Airport, December 23, 2016. (Photo by Darrin Zammit-Lupi/Reuters)





Vietnam Airlines aircraft prepares for landing at Noi Bai International Airport in Hanoi January 3, 2017. (Photo by Reuters/Kham)





A JetBlue aircraft comes in to land at Long Beach Airport in Long Beach, California, U.S., January 24, 2017. (Photo by Mike Blake/Reuters)





An Emirates Airbus A380-861 on its way from Dubai to London flies over St. Moritz, Switzerland, February 13, 2017. (Photo by Ruben Sprich/Reuters)





An Airbus A380 takes part in a flying display during the 48th Paris Air Show at the Le Bourget airport near Paris, June 16, 2009. (Photo by Pascal Rossignol/Reuters)





The plane of Chinese Premier Li Keqiang and his wife Cheng Hong arrives in Wellington, New Zealand, March 26, 2017. (Photo by Anthony Phelps/Reuters)





A China Southern Airlines aircraft flies over a slum before landing at Manila's International airport May 16, 2012. (Photo by Romeo Ranoco/Reuters)





As an airliner prepares to land, a bird takes off at the Gravelly Point park near Reagan National Airport in Arlington, Va. on December 23, 2018. (Photo by Michael S. Williamson/The Washington Post)