The assessments, released at a Senate hearing in Washington, provided a reminder of the extent of the cost overruns in major weapons programs and showed how hard they can be to resolve.
The latest estimates were embarrassing to Lockheed Martin, the largest military contractor, and to the defense secretary, Robert M. Gates.
Last summer, Mr. Gates promoted the new jet, called the F-35, when he urged Congress to halt production of the F-22 fighter plane. Some senators now say they might not have made that decision if they had known about the problems with the F-35.
Christine H. Fox, the Pentagon’s top cost evaluator, said at Thursday’s hearing that the estimated price of each F-35 had jumped to $80 million to $95 million, as measured in 2002 dollars, from $50 million when Lockheed Martin was awarded the contract in 2001.
She said her office was still refining the cost estimate, which equals $95 million to $113 million for each plane in current dollars.
Under a 15-year-old law, the Pentagon has to notify Congress when the cost of military equipment exceeds the original projection by more than 25 percent.