There are so many ways that the short take-off and vertical landing (STOVL) requirement for the F-35 program screwed up the design.
Today the fat-dumpy aircraft is still trying to get through certification so initial pilot training (that is for non-test pilots) can start at Eglin AFB. There are still safety concerns.
Non-test pilots can get into a bit more trouble. Take a look at the video below where a Canadian exchange test pilot in the USAF explains how something as simple as a hard turn with an F-16 can be an issue with an asymmetric load.
What are the flight certification challenges for the F-35? At almost 5 years after the first flight, they seem to be many.
Which makes you wonder how this 2007 flight test schedule could have been anything more than wishful thinking.