Costs are skyrocketing for the F-35 Joint Strike Fighter, the stealth plane that the Pentagon has committed to buying for generations to modernize U.S. air attack fleets, congressional auditors reported.

Total acquisition costs are now projected to be $395.7 billion, up by 42 percent from the prior estimate in 2007, according to the U.S. Government Accountability Office, auditing and investigative arm of Congress. The cost per plane has doubled from when development began in 2001, the GAO noted.

The United States has committed to buy 2,457 of the aircraft through 2037 to modernize the fleets of the Air Force, Navy and Marine Corps. Eight U.S. allies also are committed to the F-35.

The Obama administration’s decision to delay some purchases will make the aircraft more expensive in the long run, GAO officials said in a report released Thursday.

There are delays in developing and integrating software, and development of critical combat mission systems is behind schedule, the GAO reported. Aircraft deliveries are on average more than a year late, the auditors found.

The program’s challenges are creating doubts about whether it can meet critical dates for delivery, the GAO said.

“Affordability is a key challenge — annual acquisition funding needs average about $12.5 billion through 2037 and life-cycle operating and support costs are estimated at $1.1 trillion,” the GAO’s report said.

The government’s share of the F-35 program’s increased cost is $672 million, adding about $11 million to the cost of each of the 63 planes to be delivered under initial contracts, the GAO found.

The Joint Strike Fighter program office is in Crystal City, Va. The Aeronautical Systems Center at Wright-Patterson Air Force Base supports the Air Force portion of the program.

The administration’s decision to stretch out purchases of the plane to future years makes cost increases inevitable, as opposed to increased production in early years that could reduce per-unit costs, said Richard Aboulafia, a defense industry analyst with Teal Group Corp., of Fairfax, Va.

Lockheed Martin Corp., prime contractor for the F-35, said it is reviewing the GAO’s report and is working to address the concerns.

Contact this reporter at (937) 225-2242 or jnolan@DaytonDailyNews.com.