I've known a couple of pilots I thought were nuts, but I've never seen a plane run on them. Virgin Atlantic has flown the first commercial flight in a biofuel-powered jet. One tank on the London-to-Amsterdam test flight (no passengers aboard) held a biofuel mixture of coconut and babassu oil. The flight was uneventful.
COMMENT: I'm not sure whether this is a useful experiment or a good PR stunt on Richard Branson's part. Biofuel advocates often fail to tackle the hard questions about what kind of infrastructure is needed to grow, process, and ship useful quantities of said fuel, and Branson said nothing about it in connection with this flight.