Even the 'greener' greenies are a bit embarrassed by the carbon trading scam...it is merely industry hoping on the bandwagon to appear green while making a few $ for themselves.
All these sorts of things produce new industries that cost us money for no return. Y2k was a boomtime for IT, the rediculous DDT ban was a boom for chemical companies, the asbestos scare campaign gave birth to the asbestos removal industry despite the VAST majority (100% of asbestos in public buildings and school in the US) of asbestos was virtually harmless white asbestos...and now we have carbon trading care of the AGW scare campaign.
You can bet that any airline 'thoughtfully' making this available to it's passengers (to appear green-marketting fluff) will be creaming off a % as a handling fee...and they will be improving their bottom line as a direct result.