After six months of war in the Middle East, the Gulf's major aviation hubs are navigating turbulence as a hefty portion of their lucrative transit traffic opts for other airports such as Istanbul.
Between April and June, business for Middle Eastern airlines — measured by passenger kilometres — was down 30%, with that figure down close to 50% on routes to Europe, according to the International Air Transport Association (IATA).
In Dubai, the number of flight seats scheduled was down 15% year on year in August, the biggest drop among the world's top 10 airports, aviation data specialist OAG said, though the UAE hub remained the world's leading international airport by that measure.
The shock to the Gulf is significant because the region had made connecting travel a linchpin of its economic strategy.
As recently as last year, nearly one in six connecting passengers worldwide passed through the Middle East.
These travellers represented nearly half of all traffic through Dubai and the UAE capital Abu Dhabi, and almost three-quarters of traffic through Doha.
Since the outbreak of war on February 28, airspace restrictions over Iran and Iraq have taken a toll.
Risk-averse European carriers have cut services to the region, making Turkish Airlines "the big winner", according to Paul Chiambaretto, an air transport specialist at France's Montpellier Business School.
With Russian airspace also off limits to many Western airlines, Istanbul's strategic location has made it a desirable alternative, placing it at the "global centre of gravity for air transport", Chiambaretto said.
Istanbul is able to connect Europe to Asia with only a slight detour, he added.
Turkish Airlines' customer base is up 5% since the start of the conflict, with a decrease in capacity on Middle East flights offset by a 6% bump on routes to Europe and a 16% rise for East Asia.
The national carrier has been "expanding strongly for several years, offers a very good product and relies on a modern airport", Chiambaretto said.
In July, Istanbul's main airport even overtook London Heathrow with more than 8mn travellers.
The question is whether passengers will return to the Gulf once the situation stabilises.
Early last month IATA was still describing the diversion of traffic as likely a temporary phenomenon. But the longer the conflict lasts, the greater the risk that these new aviation habits will become entrenched.
In the longer term, the Gulf hubs and their reliance on connecting flights are also under threat from the arrival of a new generation of aircraft capable of flying farther.
Single-aisle jets such as the Airbus A321XLR can now fly 11 hours carrying 200 passengers. They can make direct routes between secondary cities profitable without passing through a hub, such as a route announced by United Airlines on Tuesday from Washington to the French city of Toulouse, which will begin in April 2027.
Ultra-long-haul flights are also bypassing stopovers. Australian airline Qantas plans to launch at the end of next year a 22-hour non-stop flight between Sydney and London using specially configured Airbus A350s.