“We are offering our pilots voluntary programs for the month of May to reduce excess staffing,” a United spokesperson said in a statement to NPR, attributing the decision to “recent delays in Boeing deliveries.”

United says it won’t have to cut flights.

The effort to trim pilot staffing is the latest sign that production problems at Boeing and its suppliers are rippling through the aviation industry. The plane maker has been forced to reduce deliveries of its 737 Max jets after a door plug panel blew out in midair during an Alaska Airlines flight in January.

Boeing says it’s slowed production at its factory near Seattle to focus on quality and safety, as regulators at the Federal Aviation Administration push the company and its supplier for a plan to fix widespread manufacturing problems.

The launch of the larger 737 Max 10 model has also been delayed indefinitely. United had been expecting to begin receiving those jets this year, but is now considering other options to replace them.

“Deliveries are going to be way behind what they expected,” United CEO Scott Kirby said at an investor conference last month, confirming that the company has looked into buying additional planes from Boeing’s rival, Airbus