What type of airship is it?
What gas is the airship filled with?
How long can you fly for?
Where can you fly from?
How high/low can you fly?
Can the airship fly indoors?
What air regulations apply?
Helium.
A non-flammable, non-explosive, non-toxic, inert gas (the same gas is used in party balloons - except we use a heck of a lot more!).
