The BBC are calling them 'jump jets' too now? Christ, talk about dumbing down.
The X-35 project was a dead duck right the way through the Joint Strike Fighter program, it never worked, Boeing's X-32 was a far superior aircraft, cleared tests long before the 35, and would have cost less. Unfortunately due to the US government preferring Lockheed, and Boeing's financial situation at the time they settled on the 35. It's a shame really, because the 35 can only carry two air to air weapons plus cannon, which is about as useful as throwing chocolate teapots at the enemy.
This has been going on for 11 years now, and we could have made the X-35 at BAE a long time ago if the Americans trusted us with the designs. Unfortunately they don't.
The ironic thing is that before the merge of the programs, this was called the "Common Affordable Lightweight Fighter Program" whereas in reality it's about $200 billion over budget, and the X-35 weighs 2 tons more than an F-15.