If they can show "Swiss Railway Journeys" it surely must be possible to get a reasonable customer base/profile for aviation progs ??
I said exactly the same thing whilst watching it last night! Don't knock it though; it's surprisingly compelling viewing. Though last night's episodes were repeats of ones I'd seen before..
I know very little about this, but I recall reading a website some time ago that described the exact process you would go through to create your own channel on Sky (unfortunatey I can't find the link now). IIRC it wasn't prohibitively expensive for a small organisation to broadcast it's own content through the Astra satellite network, but that a listing in the EPG and the other managed services provided by Sky would cost quite a bit more. Presumably not an awful lot more though, if some of the more niche channels are anything to go by; Psychic TV anyone?
I think there would be a considerable market for a civil-focussed aviation channel (military flying is already fairly well covered by Discovery as mentioned above). Some flight tests, airfield reviews etc for GA and a smattering of the heavy metal commerical would probably tear me away from Swiss Railway Journeys for a while.