A design flaw has left a fighter jet that 's part of the Pentagon 's most expensive project ever incapable of carrying 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 . 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 F-35 program will reportedly cost a whopping $ 590 billion over the next decade . 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 F-35B is one of three variants of the F-35 program , which has proved expensive and troublesome to get off the ground . The F-35B features a lift fan that will allow it to make short takeoffs and vertical landings , Inside Defense reported . In the US , it will be used by the Marine Corps . However , the F-35B is the centerpiece of the British Royal Navy 's new aircraft carrier-based fleet . The Ministry of Defense 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 . The F-35 program has been plagued by massive cost overruns and delays . Joe DellaVedova , a spokesman for the F-35 program , said in an Inside Defense interview last week that changes are being made to the F-35B 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 . 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 .
Fighter jet F-35B 's internal weapons bay is too small for a Small Diameter Bomb II ( SDB II ) load . Though it 's mandated that an F-35B hold eight SDB IIs in the bay , only four can reportedly fit . A F-35 program spokesman has said changes are being made so the fighter jet can be released on schedule . The SDB II can employ a number of techniques - including imaging infrared , laser , and radar homing - to hit targets . The F-35 program will cost $ 590 billion 590billion over the next decade . F-35B is slated to be used by the British Royal Navy on the HMS Queen Elizabeth aircraft carrier .