I'd like to see a complete run down of the specifications for it. Things like:
* Total weight
* Prop diameter and pitch
* Battery chemistry, voltage, mahr and weight
* Motors
* Max flight time
I believe the minimum distance between England and France is 21 miles and at 30mph that would imply at least 42 minutes and probably longer -- as I recall they took off but before starting across they hovered for a minute or two to upload the waypoints etc. They may have traveled a bit slower given they appeared to be using inflatable pontoon boats and I'm not sure how fast they can be expected to go over open ocean.
I'd guess the max flight time mat have been closer to an hour and the actual time in the air closer to 45 minutes.
Brian