In reply to SiWood:
Read this thread, lots of useful stuff:
http://www.tetongravity.com/forums/showthread.php/232272-Mammut-RAS-airbags
And as regards air travel, read this:
http://shop.snowshepherd.co.uk/epages/es122028.sf/en_GB/?ObjectPath=/Shops/...
If you're intending to buy more than one bag (say, a little one for lifts and a big one for huts) they're well worth it. If you're just after one big bag, the RAS Pro bags are probably some of the best 35-45l airbags on the market. If you're only after a single smaller bag, I'd consider looking elsewhere... the snowpulse airbag design looks much nicer to me.
You can take gas bottles on planes (IATA rules allow it, for example), but you'll need to be prepared ahead of time and getting written approval from the airline can make your life much less stressful cos the staff on the ground don't always know the rules.