The competing engines are just one component of the F-35 Joint Strike Force program -- one of the most costly weapons programs in U.S. history. The original plan called for the development of 2,443 "fifth generation" planes of three different types: planes using conventional landings, planes capable of use by the U.S. Navy on aircraft carriers, and planes capable of vertical take-offs similar to that of the famed Harrier jet.
Each of the planes ordered from aeronautics manufacturer Lockheed Martin in 2002 was originally projected to cost just over $40 million. That figure has risen nearly 25 percent, according to Lockheed Martin, to closer to $49 million, accounting for inflation over the past nine years. With inflation added, as well as additional production, maintenance and spare parts costs, the total cost per plane tops out at $92 million.
The program has also been delayed several times and recently the contract with Lockheed Martin was extended from its original 2011 deadline to 2016.
"I think what you have to recognize is this is by far the most complex aircraft ever built," Lockheed spokesperson John Kent told ABC News. "We all acknowledge that we underestimated the complexity of developing the airplane. Hindsight is always very clear and I'm sure there are things we would've done differently.
"Yes, we're behind schedule. Yes, we're over budget on developing the airplane, but we exceeded flight test milestones last year. A lot of the problems that were dogging [the project] have been fixed," he said.
GE has pointed to the delays, and what it says are $2.5 billion in cost over-runs with the Pratt & Whitney engine, as proof that an alternative is needed. Warren Boley, president of Pratt & Whitney's military engine division, calls the figure misleading and says he finds it "disappointing" that "they are throwing rocks at us."
As for whether the fighter will emerge with one brand of engine or two, Boley says he has stopped trying to predict.
"I'm not sure I'm smart enough to handicap that race," he told ABC News. "The secretary of defense is very determined. But there are those in Congress who are also very determined."