By Marina Malenic

F-35 Joint Strike Fighter flight tests resumed on Oct. 5 after corrections were made to a software flaw with the jet’s fuel pumps that resulted in a four-day grounding, according to prime contractor Lockheed Martin [LMT].

“Over the weekend, we loaded the software solution onto the flight test aircraft,” company spokesman John Kent said via email. “This morning we received clearance to fly the two aircraft at Edwards” Air Force Base, Calif.

The aircraft were grounded on Oct. 1 after ground testing revealed software defects. The code that controls the engine’s three fuel boost pumps was corrected over the weekend.

Lockheed Martin is developing three variants of the jet–a conventional takeoff and landing A model for the Air Force; a short takeoff and vertical landing B model for the Marine Corps; and a carrier variant C model for the Navy. The United States also has several international partners on the venture.

The Pentagon plans to buy 2,473 F-35s, and eight international partners are expected to buy another 700.

Pentagon Press Secretary Geoff Morrell said during a briefing this week that the software problems that caused last week’s grounding are not considered serious by the military program manager in charge of the F-35. Morrell said Vice Adm. David Venlet “does not believe this is a serous setback.”