[LeGrande]

And in the early 20th century some said the Wright brothers would never fly.

Hydrogen is not a source of energy (unless you are thinking fusion). At best it could be a good battery, but that would help : )

I have done that calculations and I think I can get more energy out of compressed air than I can out of compressing hydrogen and burning it (including the energy cost of making the hydrogen).

[RightWhale]

Of course. We’re not looking at efficiency so much as getting more than a dozen miles down the road.

[HangnJudge]

I have done that calculations and I think I can get more energy out of compressed air

Already done
Tata Motors - India

http://www.theaircar.com/acf/air-cars/air-cars.html