>>Of course, it has the major limitation that it's entirely dependent on
>>the availability of the Avatar to provide its main thrust.
>
>And the Comet. The biggest headache the Phoenix Flight mission
>planners faced was that the launch window was >< that wide, and there
>was only going to be one of them per century.

That is indeed a pretty major limiting factor. Kinda makes the likelihood of repeat flights pretty much nil.

Unless they can come up with a different arrangement, maybe multi-stage with teams of firebenders working in synch... gonna be difficult.