Whilst not exactly an "Airline Experience" I got to fly in the Belgacom gas balloon (F-GXLS) today, along with my son. Being such a sunny and clear day we got a great view over the whole of Brussels for about 10 minutes.
This was my first flight in a balloon (not sure whether it really counts as a flight as the balloon is tethered to the ground by a thick steel cable!) but it was great fun and only 10 Euros. ( I suppose I could have flown a lot further with Ryanair for about the same money!!!)
If you have never seen Brussels from the air then I can recommend the experience.
Meerkat