The leaders of the Senate Armed Services Committee are taking Defense Secretary Leon Panetta to task for undercutting their work on the Lockheed Martin F-35 Joint Strike Fighter — not once, but twice.

On Jan. 20, Panetta lifted probation on the F-35B, the Marine Corps short-takeoff-vertical-landing variant of the jet, just about one year after the time-out, originally anticipated to be in place for two years, was imposed.

Sens. John McCain (R-Ariz.) and Carl Levin (D-Mich.) say that decision appears “premature,” in a Feb. 6 letter. And the probation decision came shortly after the Pentagon moved forward with negotiations on the fifth production lot of JSFs, while the committee was working to include criteria for lifting probation into its defense authorization bill.

“We are seriously concerned about the lack of notice and consideration,” write McCain and Levin, who say they learned about both decisions from the press.

The letter comes one week before Panetta will testify before the committee on the fiscal 2013 budget request, teeing up yet another controversial issue for the Feb. 14 hearing.

But it also comes after the late November release of the “Quick Look Report” that called for a “serious reconsideration of procurement and production planning,” after the Pentagon’s director of operational test and evaluation reported that the program was not on track to meet operational effectiveness, and after 15 test versions of the F-35 were grounded for improperly loaded parachutes in their ejection seats.

“We appreciate that the development of F-35B has enjoyed some success over the last few months, after several years of having fallen short,” write Levin, the committee chairman, and McCain. “We similarly understand that engineering solutions to known problems with the F-35B’s structure and propulsion have been identified. However, in the intervening time since probation was imposed, more problems with the F-35B’s structure and propulsion, potentially as serious as those that were originally identified a year ago, have been found. This is salient where the F-35B has completed only 20% of its developmental test plan to date. Your decision, therefore, appears at least premature.”

The letter includes 14 specific questions for Panetta, including whether the Pentagon’s technical experts “specifically” participated in reaching the decision to lift probation and whether improvements in the bulkhead, the auxiliary inlet door, the lift-fan clutch, and the lift-fan drive shaft had improved enough to merit being removed from probation.

“We continue to be frustrated that the Department is failing to communicate with this committee on key developments relating to this program and ask that you rectify this problem as soon as possible,” the senators write in the Feb. 6 letter.

Along with the letter to Panetta, the senators are calling on the comptroller general to review the extent to which the program has resolved the issues that former Defense Secretary Robert Gates had flagged when he placed the program on probation, and to describe the extent to which any additional structural or propulsion issues have cropped up since that time.