A new Pentagon study has validated previous findings that Lockheed’s F-35 Joint Strike Fighter aircraft will require billions of dollars more than planned, as well as more time.

The F-35 is a fifth-generation stealth fighter being developed by Lockheed for a consortium of US and allied nations to replace at least 13 types of aircraft for 11 nations initially.

The US intends to acquire about 2,443 F-35s, while purchases by partner nations the UK, Canada, Italy, Denmark, Netherlands, Norway, Turkey, Australia and others could raise production to 3,000 or more.

The study, which updated the study undertaken in 2008, found the programme would need at least two more years and nearly $15bn more, according to Reuters.

The Weapons Systems Acquisition Reform Act that became law in May 2009 requires the Pentagon to presume termination of any programme that breaches certain cost targets.

This implies that if the Pentagon wants to retain the F-35 programme, it would have to restructure and recertify the weapon acquisition law.