Willie Walsh, director general of the International Air Transport Association, told Reuters the topic had been raised by “every single one” of the airline CEOs he had met as the industry gathers for a three-day annual meeting in Istanbul.

Airlines “are not concerned about the macroeconomic environment, they’re concerned about the access to spare parts for their existing aircraft and the delivery of new aircraft. So it’s definitely got to hold back capacity growth,” he said.

“It’s frustrating because airlines can see strong demand, but they’re not able to match supply with demand in many markets. And this is something we want to see resolved.”

Airbus (AIR.PA) and Boeing (BA.N) have blamed supply chains for delivery delays, while bottlenecks in a network of engine repair shops have also forced airlines to ground dozens of jets.

The gathering comes two weeks before the Paris Airshow, where supply pressures are likely to overshadow new orders.