It's another sign the Air Force may have to keep planes in the air years longer than originally planned while it flies the smallest and oldest fleet in its history.
The average age of an Air Force plane is 27 years. In the interim, the aircraft have continuously flown combat missions for decades, and finding parts often becomes harder as the planes grow older, officials say.
The job to acquire, maintain and modernize more than 2,000 aircraft lands on the Fighters and Bombers Directorate at Wright-Patterson, a workforce of about 3,000 people across the country, said Brig. Gen. Michael J. Schmidt, who since April has been the directorate program executive officer.
Consider that the last B-52 Stratofortress rolled off the assembly line in 1962; the A-10 Thunderbolt II, F-15 and F-16 Fighting Falcon first flew in the 1970s; the B-1 Lancer in the 1980s; and B-2 Spirit bombers have flown two decades.
"If you think about those (aircraft), to get those initial operation capability dates, the technology in them was older than that," Schmidt said. "(It's a) huge amount of work in sustaining these legacy fleet of aircraft."
About 20 percent of B-1 bombers, for example, have a parts issue at any one time, a rate about twice as high as other military aircraft, he said.
"Out-of-production parts and vanishing vendors are things that we deal with on every single program, but of course the older the airplane the harder it is to go out and find someone in industry sometimes that is either willing to do it or has the capability to do it," he said.
For some needs, the Rapid Development Integration Facility at Wright-Patterson has made equipment, Schmidt said.
At the same time, the Air Force faces a shortage of skilled workers in maintenance depots, the one-star general said. More than 25,000 employees work in three Air Force depots at bases in Georgia, Oklahoma and Utah.
Eagle in the skies
The Air Force has started fatigue testing of the F-15 to determine if it can as much as triple the original life span, Schmidt said.
"We're going to figure out through this fatigue testing process what things are breaking and how much do we have to invest to sustain that airplane to maybe three times the life cycle and then make some decisions on whether we can afford to do that," Schmidt said.
One of the reasons the Air Force needs to fly the F-15 longer is because it bought far fewer F-22 Raptors meant to replace the F-15, an aviation analyst said. Another is a slower-than-expected pace to buy the F-35 Joint Strike Fighter, which the Air Force expects to declare ready to join the fleet later this year after years of delays and technical challenges.
Eventually, the F-35A will replace the A-10 and F-16.
"The early death of the F-22 program, along with slower-than-expected F-35 procurement, means that last generation just simply have to last longer," Richard Aboulafia, a Teal Group analyst in Virginia, wrote in an email. "Since the F-15 is a great all-around fighter and strike aircraft, it will stay in service for decades to come."
In recent weeks, congressional lawmakers have asked the Air Force to explore restarting production of the Raptor. Once envisioned to field a fleet of 750 fighters, the Pentagon slashed the number to 187 out of budget concerns and the last stealth fighter was built in 2011.
Schmidt said he would let the decision-makers determine the need for the jet, "but the longer we wait the more expensive it gets and the harder it gets to reconstitute that group of suppliers."
Connecticut-based Pratt & Whitney, for example, no longer assembles the jet's engines, he said.
Keeping the F-15 flying through 2040 depends on how threats evolve, what missions are highest priority and the cost to keep the plane airworthy, another defense analyst said.
"Older F-15s are already gone from the force, because you can't fly tight maneuvers at supersonic speeds for decades without it taking a toll on the aircraft," Loren Thompson, a defense expert with the Virginia-based Lexington Institute and a defense industry consultant, wrote in an email.
"It isn't clear that non-stealthy planes like the F-15 will be able to safely transit hostile airspace 30 years from now -- even with upgrades like new jamming equipment," he added.
Like the F-15, the Fighters and Bombers Directorate modernizes aging planes with updated communications, radar, navigation and defensive systems and weapons and manages foreign military programs of Air Force aircraft sold overseas, such as F-15s to Saudi Arabia, F-16s to Iraq, and the A-29 to Afghanistan and Lebanon, Schmidt said.
The directorate has pushed program managers to work with the defense industry to install new aircraft technologies more quickly through an "open architecture" and worked with small businesses to bring in innovations, Schmidt said.
Air Force depots also have added new capabilities, such as work on F-16 computer software, in recent years, he added.