The Marine Corps has completed sea trials for the F-35B Lightning II that included the first testing of the short take-off and vertical landing aboard a ship, Naval Air Systems Command (NAVAIR) said.

The 18 days of trials were conducted aboard the USS Wasp (LHD-1) amphibious assault ship, where two of the Joint Strike Fighter logged more than 28 hours of flight time and conducted 72 short take-offs and vertical landings (STOVL), NAVAIR said.

The tests were a key step for the Marine Corps and its effort to ensure its F-35B variant meets a two-year timeframe for removing the program from probation. Then-defense secretary Robert Gates announced the probationary period in January intended to give the program to get on track.

The tests are designed to collect data on the F-35B’s ability to perform sea-based short take-off and vertical landing (STOVL), and to determine how the plane integrates with the ship’s landing systems and deck and hangar operations. Lockheed Martin [LMT] is the prime contractor for the F-35s.

The Marine Corps’ F-35B has been the most troubled of the Joint Strike Fighter variants, although the Air Force and Navy versions have also faced heavy scrutiny on Capitol Hill for cost overruns and delays. The Marine variant has been further complicated by the difficulties associated with STOVL.

The Senate Armed Services Committee (SASC) deferred recently on a Pentagon request to shift $179 million from other programs to cover cost overruns for the F-35 (Defense Daily, Oct. 18, 2011).

The F-35B trials were the first of three planned sea-based tests. The second round is scheduled for 2013, after the Wasp receives additional modifications for F-35B operations, NAVAIR said.

The LHD-1 returned to its homeport of Naval Station Norfolk Oct. 21. The first F-35 B vertical landing on Wasp took place Oct. 3 and the first short take-off occurred on the following day.

The F-35B is slated to replace the Marine fleet of AV-8B Harriers and F-18 Hornets.

Lt. Gen. Terry Robling, the Marine Corps chief of aviation, told a Navy League-hosted breakfast in September that he expected to resolve 80 percent of the plane’s major challenges by the end of this year (Defense Daily Sept. 30, 2011).

Still, Robling said the timeframe for achieving initial operational capability (IOC) has likely slipped from 2014 to 2015 after already encountering a three-year delay. The Marine Corps plans to get the first training aircraft in November at Eglin AFB, Fla. Training, which had been set for March 2012, will likely be pushed back a few months, he said.