The Air Force’s future $16.3 billion program to replace its training aircraft has seen each of the so-called “Big Five” defense contractors express an interest in the competition.

It has also seen three of them drop out of the running.

Of those defense giants, only The Boeing Co. (NYSE: BA) and Lockheed Martin Corp. (NYSE: LMT) remain in the Air Force’s Trainer-X competition. General Dynamics Corp. (NYSE: GD) first bowed out in April 2015, with Raytheon Co. (NYSE: RTN) announcing its exit in January and Northrop Grumman Corp. (NYSE: NOC) abandoning the program the week after. Textron Airland also announced that it too would not enter the fray, Defense News reported Tuesday.

So, why do the majority of big name defense companies want out? Given that the Air Force has already awarded contracts for the fighter, tanker and bomber— with not many major programs out on the horizon — one would think they would be clamoring to build the 350 trainers.

Richard Aboulafia, vice president of analysis at the Fairfax-based Teal Group and an aviation consultant, argued that the dearth of major future Air Force programs may actually be what’s behind all these companies leaving the field.

The Air Force, he said, likely took note of this environment marked with "not many aircraft contests" where "everyone is eager to win something” in drafting the request for proposals, allowing it to “extract the best possible terms based on the acquisition side.”

“They basically put forth a contract where you’re not reimbursed for development,” Aboulafia said. “It’s a price-shootout with a little window dressing. You get an incentive for performance but in the broader context of the cost of the program it’s almost insignificant.”

WASHINGTON — With U.S. President Donald Trump’s attention fixed on the F-35 and Air Force One, the Air Force’s biggest ongoing aircraft competition so far has gone untouched. But even without Trump’s intervention, the T-X race has evolved into something not unlike an episode of a reality TV show, featuring industry teams breaking up, companies unexpectedly dropping out and upstart entries coming in at the last minute.

The T-X program began with four main competitors: Lockheed Martin, Boeing, Northrop Grumman — which developed a new prototype — and a Raytheon-Leonardo team offering the latter firm’s M-346. Over the past couple of months, Northrop has pulled out of the competition, Raytheon dissolved its partnership with Leonardo — leaving the Italian firm to ally with its US wing, DRS Technologies — and several smaller companies, including Sierra Nevada and the nigh-unknown Stavatti Aerospace, decided to throw their designs into the ring.

Analysts tell Defense News that the drama overshadows the most important point: The competition has become a face-off between Boeing’s clean-sheet T-X design and the Lockheed Martin-Korean Aerospace Industries’ T-50A, the US derivative of a trainer flown by the South Korean, Iraqi, Philippine and Indonesian militaries.

"It looks like the emphasis is still very much on unit price and not much of anything else. It's [lowest price technically acceptable], basically, but with some window dressing,” said Richard Aboulafia, an analyst with the Teal Group. “And given the need to roll up the upfront development costs, Boeing is at a disadvantage. They'd have to be very aggressive price-wise. They obviously have a history of doing that with [the KC-46] tanker, but this clearly puts the advantage with Lockheed."