CAPITOL HILL: The Pentagon’s most expensive conventional weapon program emerged largely unscathed from perhaps its most intensive review before the crucial congressional subcommittee that controls military funding. As over budget and behind schedule as the $391 billion, 2,443-plane F-35 program has fallen since initial promises of a low-cost, multi-service Joint Strike Fighter, two high-powered panels of witnesses told the Senate Appropriations defense subcommittee that there was no alternative to the F-35.

It was an extraordinary lineup: The four-star chiefs of the Air Force and Navy; the four-star Assistant Commandant of the Marine Corps; the three-star heads of the F-35 program; the Defense Department’s top tester and top acquisition official; the Government Accountability Office’s top acquisition expert; and a lone thinktanker, the Brooking Institution’s widely cited Michael O’Hanlon. But it was also telling just how lackluster attendance was on the part of the legislators who had convened all this starpower. Just six of the SAC-D’s 19 members bothered to show up, and one, Alaska’s Lisa Murkowski (R), only wanted to question the Air Force Chief of Staff about plans to remove F-16s from her homestate’s Eileson Air Force Base. (The House Armed Services Committee has rejected measures to dial back the F-35 program as well).

[Click here to read about Under Secretary Frank Kendall’s admission of the damage done by Chinese hacking of the F-35 program.]

The questions left unanswered by the hearing were when the three variants of the high-tech stealthy fighter – the Air Force F-35A, Marine Corps F-35B, and Navy F-35C — would become truly combat ready (as opposed to just “initial operational capability” or IOC), how much they would cost to buy, how much to maintain, and how many can the nation afford. That’s an especially complex calculation because buying fewer aircraft doesn’t affect fixed overhead costs, so the price per plane goes up as the number of planes goes down. Many thinktanks have called for a smaller F-35 fleet, and at the hearing Brookings’ O’Hanlon argued for a force of only about 1,250 to meet the high-end threats, while buying more older, so-called legacy fighters to handle other needs. But, he acknowledged, the reduced buy would drive up unit cost so the 50 percent cut in total buy would only provide about a 20 percent savings.

As is the case with many of the futuristic weapons programs, the biggest uncertainty on making the F-35 operational was the ability to develop and test the sophisticated computer software that made the fighter what one witness called “a flying computer.”

The program executive officer, Air Force Lt. Gen. Christopher Bogdan – who once said the military’s relationship with contractor Lockheed Martin was “the worst I’ve ever seen” – said he was “cautiously optimistic” that Lockheed Martin and its suppliers could produce the block 3F software necessary to make the jet combat ready by 2017, when all three of the participating services expect to declare full operational capability.

In his first major initiative as chairman of the crucial subcommittee Sen. Dick Durbin noted that the F-35 “has had more than its share of problems” and served as “a text book example” of the Pentagon’s procurement woes. Durbin challenged the witnesses to tell him what they have learned from this experience and what they were doing to ensure it would not be repeated. He also wanted to hear “if any alternative is being considered for a less costly fighter.”

He received a mixed answer to the first set of questions. But on the second, there was agreement even among the program critics that it would be impractical and wasteful to start over again after investing more than 12 years and $44 billion on the Lockheed-built jet.

“I don’t believe we have any alternative but to make the program work” said one of the program’s toughest critics inside the Pentagon, Michael Gilmore, director of Defense Operational Test and Evaluation.

That view was shared by top officials from the three services that are depending on the F-35 to freshen their air combat fleet, on average the oldest in the nation’s history.

Gen. Mark Welsh, chief of staff of the Air Force, which expects to buy more than half – 1,763 – of the 2,443 F-35s the Pentagon plans to obtain, said the new fighter was “essential to ensure we can provide that air superiority” that has prevented a single U.S. ground troop casualty since the Korean War. With potential adversaries developing new advanced aircraft, Welsh said, “the Air Force needs the F-35A to ensure we can keep the air battle an away game. “It is the only conceivable program” to do that.

Adm. Jonathan Greenert, chief of naval operations, said the carrier-capable F-35C is a “really key part of our future” and will bring an “essential and unique set of capabilities for our air wings.”

“We need the stealth, we need the advanced electronic warfare capability” and its ability to collect and share intelligence, Greenert said. “The F-35C is designed to provide the capabilities we need.”

But, Greenert added, the Navy needed the Block 3F software, “an arresting hook that is reliable,” and a helmet that works. The admiral was referring to the fact that the tailhook on the initial model of the F-35C failed to catch the thick cables that bring an aircraft to a stop on an aircraft carrier’s short landing deck, and the pilot’s helmet was unable to provide the clear view of aircraft performance and external conditions required for combat operations.

And, Greenert said, “I need to know how much it will cost to maintain” the aircraft once it is in the fleet.

That was one of the key unknowns identified by Bogdan and other program officials.

Gen. John Paxton, the assistant Marine Corps commandant, said the short takeoff, vertical landing capability of the F-35B, which can operate from large deck amphibious assault ships and from small, crude land bases will double the number of aircraft-capable ships the Navy has and can put fighter aircraft in close support of ground Marines.

The Marines need the F-35 badly because it would replace their F/A-18s, EA-6Bs and AV-8Bs, all of which are at or over their expected service life.

In the first panel before the committee, Kendall and Bodgan acknowledged the major problems with the F-35 program due to excessive “concurrency,” which means the program began production of supposedly operational aircraft before flight testing has worked out all the kinks in the design – a shortcut Kendall has in the past called “acquisition malpractice.”

They agreed that the program has made significant progress since it was drastically revamped and production was slowed. The design now is stable, production processes have improved, unit costs are coming down and the flight test program is providing reams of data that will make it possible to provide better information to continue to improve and to develop ways to reduce the cost to sustain the jets once they are in service.