When Pigs Fly
I agree. This could be a bit like the toaster challenge. In the true spirit of all things FT, the Flying Pig challenge could work something like this:
1) The participants each have to agree to do something they wouldn't normally do "When pigs fly"
2) The flying machines should look very unlikely to fly, and more at home in a puddle of mud.
3) Extra points for wacky originality.
I can picture the FT crew having a lot of fun with this idea!