Fighter jets about-turn 'will harm capability Because of the shortfall in jump jet capabilities, the MoD will have to spend an extra £2.4 billion buying 136 aircraft compared with 97 of the conventional planes, the paper adds. Defence planners overseeing top-secret "scenario planning" for potential future military missions have concluded that in every one of the operations that the Armed Forces is likely to have to undertake in the coming years, the new jet is less useful than the original one. The document, an "Operational Analysis Supporting Paper" prepared by the Defence Science and Technical Laboratory, warns that the jump jet has "considerable technical risks." The "key issue" is that it carries far less fuel than the conventional plane, meaning it can carry fewer weapons and not fly as far. The reduced range means the jump jet can spend less time over its target than the conventional jet. For a target 300 nautical miles away from the aircraft carrier, the jump-jet can spend only 20 minutes over its target before turning back, compared with 80 minutes for the conventional jet. The paper also reveals the findings of a sensitive planning exercise for a range of possible future missions. Scenarios include a "medium-scale enduring stability operation" in Saudi Arabia, in conjunction with allies; British operations in Afghanistan continuing until 2025, with warplanes deployed for a decade after Mr Cameron's deadline for an end to combat operations; a mission to retake the Falklands after a successful Argentine invasion, which states that "the conventional variant [fighter] provides a more robust capability." The MoD said no decision had been made on switching to the jump jet, and played down the paper's findings. A spokesman said: "As you would expect, the MoD works up a wide range of scenarios, many of which are highly unlikely, to scope contingency work as fully as possible." He added: "The Government has been clear that UK combat operations in Afghanistan will cease by the end of 2014."