* The cost of operating and sustaining the new planes is estimated to reach $1.1 trillion, assuming that they will be used for 50 years, according to the most recent Pentagon data, although those estimates are likely to be updated this fall.
* Senior Pentagon officials have said they consider that price tag unaffordable. Program officials are taking steps to reduce the projected operating cost, including hiring engine maker Pratt & Whitney, a unit of United Technologies Corp (UTX.N), to cut the fuel burn of the engine by 5 percent.
COST PER JET
* New cost estimates prepared by the Pentagon showed a drop in the projected average cost of the Air Force and Marine Corps variants over the life of the program, but the projected cost of the U.S. Navy variant for aircraft carriers edged higher.
* The Pentagon now forecasts that the conventional takeoff A-model will average a cost of $76.8 million per plane, excluding R&D costs, down which is $1.9 million less than the estimate provided last year. The B-model, which can take off and land like a helicopter, is slated to cost $103.6 million per plane.
* The latest estimate put the cost of the carrier variant at $88.7 million per plane, up $1.7 million from last year.
* The fifth and most recent batch of jets ordered by the Pentagon cost 4 percent less than the previous order, and prices should come down steadily in the future, according to Air Force Lieutenant General Christopher Bogdan, who runs the F-35 program for the Pentagon.
* Lockheed submitted a bid for the next two batches of jets in January and both sides hope to reach agreement this summer.