Military challenged to maintain decades-old aircraft.

• Author: Erwin, Sandra I.

The U.S. military operates fleets of Cold War-era aircraft that will not be replaced any time soon. For the Pentagon, this creates daunting challenges, experts warn. Airplanes will have to fly much longer than planned and, at a time of tight budgets, the cost of maintaining aging equipment is projected to soar.

The Defense Department is slowly coming to grips with the situation, said retired Air Force Lt. Gen. Donald J. Wetekam. "We are in unknown territory" on how to keep aircraft flying indefinitely, he said. The Air Force, the branch of the military most affected by aging planes, expects to operate many of its aircraft well beyond their original design service lives. But it does not necessarily know how long components will last, if replacements will be available or if they can be remanufactured, said Wetekam, a senior vice president of AAR Corp., a logistics company that does business in military and commercial aviation.

"We're in areas where we have not gone before," he said in a recent interview. When Wetekam first became an officer in the Air Force, the average age of the fleet was nine years. When he retired as deputy chief of staff for installations and logistics, that number had reached 24. Since then, the average age has inched up to 27. "That is three times what it was when I was commissioned. And at the time we didn't think we had a particularly modern Elect."

The Defense Department has a fleet of 14,800 aircraft, according to new data by Bloomberg Government. The Air Force has the largest number of fixed-wing aircraft, followed by the Navy. The Army has the largest number of helicopters and surveillance drones.

Air Force Chief of Staff Gen. Mark Welsh sounded alarms in September. "Airplanes are falling apart," he said. "There are too many things happening because our fleets are too old."

In a 30-year aircraft procurement plan the Defense Department submitted to Congress three years ago, the Pentagon projected it would be at least 10 years before new strategic airlifters and long-range bombers are produced and delivered. The KC-46A would be the only new airplane procurement though 2025, and the next-generation tactical fighter, the F-35, will not meet required force levels until 2035 at best.

A panel of experts in 2011 warned the Air Force that, in order to cope with its rapidly aging fleet, it needed to revamp aircraft maintenance to make it more efficient and less costly.

"The sustainment of aging aircraft like those in the...