A design flaw has left a fighter jet that 's part of the Pentagon 's most expensive project ever incapable of carrying the military 's most highly advanced bombs . The F-35B 's internal weapons bay is too small for a Small Diameter Bomb II ( SDB II ) load , according to an Inside Defense report . The fighter jet is the centerpiece of the British Royal Navy 's new aircraft carrier-based fleet , and dozens have already been ordered . Trouble in the skies : The F-35B 's internal weapons bay is too small for a Small Diameter Bomb II ( SDB II ) load ( file photo ) The Ministry of Defence has ordered 48 of the aircraft and they are the only fighter jets set to launch off two planned British aircraft carriers - the HMS Queen Elizabeth and the HMS Prince of Wales . Though it 's mandated that an F-35B jet , designed by Lockheed Martin , hold eight SDB IIs in the bay , only four reportedly fit . The problem will not affect the Royal Navy 's consignment of F-35Bs , however , as its aircraft are to carry different weapons . The F-35 program will reportedly cost more than £2.5billion over the next decade . The F-35B is one of three variants of the F-35 program - and it 's proved the most expensive and most troublesome to get off the ground . The F-35B features a lift fan that will allow it to make short takeoffs and vertical landings - like a helicopter . The F-35 in general - and the F-35B in particular - has been plagued by massive cost overruns and delays . The queen unveils HMS Queen Elizabeth with Prince Philip in a ceremony on the Firth of Forth in July . The ship will be launched for sea trials in 2016 . The Ministry of Defence has ordered 48 of the aircraft and they are the only fighter jets set to launch off two planned British aircraft carriers - the HMS Queen Elizabeth ( pictured ) and the HMS Prince of Wales . Since work began in 2007 , an estimated 10,000 shipyard workers and engineers have been employed in building the ship which will employ a crew of fewer than 700 once complete . Artists impressions of the ship 's flight deck released before construction was underway . When completed the vessel will have enough room for dozens of aircraft . Joe DellaVedova , a spokesman for the F-35 program , said in an Inside Defense interview last week that changes are being made to the jet so it can be released on schedule . DellaVedova also said that Lockheed Martin will likely get the alterations contract down the line in 2015 . 'This is not a new issue to us , ' DellaVedova told Inside Defense . 'We 've been working with the SDB II program office and their contractors since 2007 . 'The fit issues have been known and documented and there were larger and more substantial modifications needed to support SDB II that have already been incorporated into production F-35 aircraft . 'These minor or remaining changes were put on hold until the aircraft reached a sufficient level of maturity to ensure that the needed changes would not adversely impact any ongoing SDB [ II ] developments . ' Inside Defense reported that the Joint Strike Fighter ( JSF ) program office so far has not publicly recognized problems - and that eight internal and 16 external SDB IIs are in fact meant to go on the F-35B . An MoD spokesman said : 'The Small Diameter Bomb II is not part of the UK 's planned weapon inventory for the Lightning II . The programme to integrate weapons from the UK inventory onto Lightning II is on track to deliver initial operating capability as planned in December 2018 . ' Bombs away : The SDB II can employ a number of techniques - including imaging infrared , laser , and radar homing - to hit targets , defense contractor Raytheon says . Defense contractor Raytheon is behind the SDB II bomb . The company proclaims on its website 'SDB II can fly more than 45 miles to strike mobile targets , reducing aircrews ' time in harm 's way . 'The weapon 's small size allows fewer aircraft to take out the same number of targets as previous , larger weapons that required multiple jets . 'SDB II 's size has broader implications for the warfighter and taxpayers , as it means fewer attacks with less time spent flying dangerous missions . ' The SDB II can employ a number of techniques - including imaging infrared , laser , and radar homing - to hit targets , the company says . The SDB II weapons system is fully accommodated by both the F-35A - the Air Force version - and F-35C - the US Navy version , company executive Jeff White told Inside Defense . White told the news outlet ' I think it 's just the B . When we did our fit checks on the JSF , the A and the C basically had the same bay . ' 353 F-35Bs are being bought by the United States Marines Corps , Inside Defense reported . According to the news outlet , approximately 17,000 weapons will come from the United States Air Force 's SDB II program .
F-35B is slated to be used by the Royal Navy on HMS Queen Elizabeth . Fighter jet 's internal weapons bay is too small for a proper bomb load . F-35B is supposed to hold eight SDB II bombs in the bay , but only four can fit . A program spokesman has said changes are being made to the jet . Royal Navy 's version is not intended to carry SDB II bombs . F-35 program will cost an estimated £2.5billion over the next decade .