London, Nov 18 : A British F-35 fighter jet has crashed into the sea during a routine operation in the Mediterranean, the country's Ministry of Defence has said. The pilot ejected and returned safely to the royal navy aircraft carrier HMS Queen Elizabeth, the Ministry said on Wednesday. The incident happened at 10:00 GMT over international waters and hostile action is not thought to have been involved, it added. An investigation has begun and would likely focus on potential technical or human error, reported the BBC. There are eight British F-35 jets on the carrier and 12 from the US Marine Corps, Xinhua news agency reported. The supersonic fighters, which cost 92 million pounds (about $124 million) each and are built by the US firm Lockheed Martin, are based at RAF Marham in Norfolk, according to the BBC. /IANS