United Airlines Holdings Inc. asked pilots to take unpaid time off in May, a staffing cutback that could extend into late 2024 as the carrier grapples with delayed deliveries of Boeing Co. planes.

The delays have reduced the number of hours United had planned for its pilots to fly in 2024, and the additional time off will reduce excess staffing as a result, a spokeswoman for the carrier said in April 1. The company didn’t specify how many flight hours it hopes to trim.

The program could be extended into the summer and potentially the fall, according to a memo from the Air Line Pilots Association, which represents United pilots. Boeing delivery delays have “significantly reduced” the carrier’s flying plans, it said. 

The effort is United’s latest move to contend with a difficult year. Boeing delays have upended the carrier’s plans for the year while a series of safety incidents have drawn the attention of travelers and U.S. aviation regulators. The airline is also carrying out an internal safety review. 

The U.S. Federal Aviation Administration is examining United’s operations and considering actions that could curb the airline’s growth plans, Bloomberg reported last month. The carrier in January pulled the long-delayed Boeing 737 Max 10 from its fleet plans for the year, and has since begun to slow pilot hiring and training classes for new aviators due to the plane’s absence. 

Delayed deliveries of Boeing 787 wide-body and 737 Max single-aisle aircraft will also affect flying on other jets in United’s fleet, the union told members. The group said it will evaluate any additional future programs to curtail staffing.

United was to have received 80 Max 10s this year, part of an outstanding order with Boeing for 277 of the planes. 

The airline has been working with Boeing to convert some of the Max 10 orders to the smaller Max 8 or 9 variants to receive planes sooner, and is in advanced talks to acquire additional Airbus SE A321neo aircraft as soon as next year, Bloomberg has reported.

CNBC reported the leave offer earlier Monday.