Military officials told senators last week their services’ delayed initial operational capability (IOC) dates for the F-35 Joint Strike Fighter will be reset according to the aircrafts’ performance.

The IOC date for the Marine Corps, the first service slated to receive Lockheed Martin’s [LMT] F-35, is no longer 2012 and more likely is 2014 or 2015, Marine Corps Deputy Commandant for Aviation Lt. Gen. Terry Robling told the Senate Armed Services Airland subcommittee.

“Certainly, with this period of scrutiny (of the F-35 programs) and looking at the aircraft and the reduced ramp, we’re going to slide,” Robling told panel Chairman Sen. Joseph Lieberman (I/D-Conn.) “I think what we’ve decided to do now is not set an IOC date certain, but set a window out there. And, of course, we’re looking with a two-year slide, a slide at least two years, and probably somewhere, in (the) 2014 or 2015 timeframe.”

The setting of the new IOC will be “event driven,” Robling said. Navy and Air Force officials also told Lieberman their IOCs will be delayed, beyond previous dates of 2016, and new estimates will be determined by future events.

For the Air Force, it is a “good estimate” that the IOC of 2016 will be delayed by two years, Lt. Gen. Herbert Carlisle, deputy chief of staff for operations, plans, and requirements, told the panel.

Navy Rear Adm. David Philman, director for warfare integration, said his service believes the 2016 date is “no longer valid,” though he declined to speculate on a revised timeframe.

“Again, event-driven where we have a squadron, we have training facilities, we have, hangar facilities and all those things, as well as the logistics pipeline to support those aircraft,” Philman testified. “Then once all those are satisfied, the (chief of naval operations) CNO can declare IOC.”

In terms of setting the new Air Force IOC, just “like the Marines and the Navy, it’ll be event-driven based on how the airplanes develop and tactics training and the (operational test and evalutation) OT&E on the airplane,” Carlisle said.

Lieberman called the delaying of the IOCs “really unfortunate,” but said at the May 24 hearing that “there’s nothing you can do about that except to react to the reality of the program developments.”

The Pentagon recently delayed the start of full-rate F-35 production by a year and put the Marine Corps’ short-takeoff/vertical-landing (STOVL) variant on a two-year probation period to work out technical kinks.

After conducting a technical-baseline review of the multi-nation F-35 program, the Pentagon now estimates the aircraft’s development will take an additional one and a half years and cost $4.5 billion more than was estimated in the spring of 2010, Cost Assessment and Program Evaluation (CAPE) Director Christine Fox told the full Senate Armed Services Committee May 20. The Pentagon now estimates the average cost per aircraft is $95 million in fiscal year 2002 dollars, up from an estimate last year of $80 million derived by the F-35 program office, she said.

Two main factors that have increased the F-35’s development cost and schedule are the price of integrating software and mission systems and the cost of the Marine Corps’ STOVL variant, according to Fox.

F-35 program manager Navy Vice Adm. David Venlet started the in-depth review after taking control of the troubled aircraft effort last year.

The Pentagon is expected to release new cost and schedule data for the F-35 program following a Defense Acquisition Board review.