The Marine Corps’ top officer said recently he remains hopeful his service’s variant of Lockheed Martin‘s [LMT] F-35 Joint Strike Fighter can be removed from a two-year probation, possibly after shipboard testing later this year.

Marine Commandant Gen. James Amos said he thinks “it’s important” that the F-35B, his service’s short-takeoff/vertical-landing variant of the multi-service F-35, get out of a two-year probationary period called for in the fiscal year 2012 budget request the Pentagon sent Congress in February.

“I think we’re probably pretty close right now to qualifying for getting it out,” Amos said recently at the Institute for Defense and Government Advancement’s Amphibious Operations Summit in Washington.

His comments come as the overall F-35 program has come under intense scrutiny and criticism from the Senate Armed Services Committee (SASC) because of cost and schedule delays. Committee Ranking Member John McCain (R-Ariz.) has gone as far as to propose reforms that could lead to the program’s cancellation.

Amos, who told lawmakers as early as March he wanted the STOVL aircraft off probation in less than two years, said recently he was the person who suggested that timeframe to Robert Gates, the now-retired defense secretary, before the FY ’12 budget request was completed. The two officials discussed technical and schedule problems with the STOVL, and while Gates suggested putting the aircraft on a one-year probation, Amos said he himself proposed the two-year period.

“I was the guy who said, no sir I think we ought to give it about two years,” the commandant said recently.

Amos noted no formal definition exists for such a probation. He said he touted the STOVL aircraft’s progress to Gates shortly before his June 30 retirement, and suggested some metrics that could be used for removing the aircraft from the probation.

One of the metrics on Amos’ metrics list is shipboard trials. Two STOVLs already are outfitted with test equipment in preparation for shipboard trials later this year, he said.

“Assuming it does well on the shipboard aspect of that, then for lack of anybody else coming forward with a set of metrics to get it off probation, I think it beats it,” Amos said recently. “I’m confident we can get it off probation. It doesn’t do the program any good to be on probation now.”

Air Force Maj. Gen. C.D. Moore, deputy director of the Joint Strike Fighter program office, said recently he believes most of the risk with the program will be gone by late 2013, after which he predicted the effort will be in “calm water.”

Moore, speaking at an Air Force Association breakfast in Arlington, Va., portrayed aircraft testing as progressing well.

He said the program faces three “key challenges.” They relate to completing software development and integration on time and cost, finishing durability of full system qualification testing, and “delivering on affordability commitment for production and sustainment.”

Moore said the Pentagon delayed until the fall a high-level Defense Acquisition Board (DAB) review of the F-35 program, previously planned for May, because before the high- stakes meeting program officials want to go through a “disciplined process of assessment.”

As part of the DAB review, the F-35 program’s baseline cost, in the Pentagon’s Selected Acquisition Report (SAR) to Congress, will be updated, he said.

Shay Assad, the Pentagon’s director of defense pricing, told a Defense Writers Group breakfast in Washington recently that he is working closely with Navy Vice Adm. David Venlet, the F-35 program executive officer, to determine what the aircraft program should cost.

The revision of the F-35’s SAR figure comes after the program restructuring Gates announced in February. The Pentagon extended the F-35’s development phase, reduced the number of production aircraft delivered in the early years, and placed the STOVL variant on probation.

Meanwhile, the F-35 is coming under fire on Capitol Hill.

SASC Chairman Carl Levin (D-Mich.) and McCain told Defense Secretary Leon Panetta in a July 14 letter they have serious concerns about $771 million in cost overruns with the first 28 F-35 aircraft and a Pentagon proposal to pay part of the increased pricetag.

The senators said they would not approve a Pentagon request to reprogram $264 million within its own coffers to help cover the overrun before Panetta answers a series of questions, including what it would cost to terminate the entire program.

The SASC also put constrictions on the F-35 program in the FY ’12 defense authorization bill it approved June 16. The legislation, which the full Senate has not yet debated, states the low-rate-initial-production contract for the Lot 5 aircraft under negotiation must require Lockheed Martin pay all costs that exceed the target amount. McCain failed in an attempt to add language to the bill to put the program on probation and terminate it next year if costs are 10 percent over the target amount. He has said he may try to add that language to the bill during floor debate.