The US Marine Corps F-35 joint strike fighter has been given an additional $4.6bn funding boost and put on a two-year probation.

The funding and delay in purchase will help Lockheed to demonstrate the fighter’s reliability, which could lead to a redesign of the aircraft’s structure and propulsion.

The Marines’ F-35 joint strike fighter is designed for short take-off and vertical-landing from smaller amphibious warfare vessels, as well as landings on improvised airstrips, and will replace the 25-year-old AV-B Harrier.

The F-35, Pentagon‘s biggest weapons project, is four years behind schedule and the cost estimate per aircraft has doubled from the original $50m.

The Pentagon is developing three versions of the aircraft in the $382bn programme and the navy plans to buy 371 Marine Corps versions of the 680, according to Bloomberg.