Dear PP,
The PFT or Pay2fly is not a relatively new concept but it has been limited somewhat by the realities of the US marketplace. The only PFT scheme I am currently aware of is an outfit in Florida, called Gulf Coast Airlines, or Gulf Coast aviation.
The have a PFT scheme and flight school for the BE-1900. They fly as a code share partner for several major carriers and fly to the islands from MIA and FLL. The are the only one i am aware of right now.
Because the Regional industry was in such a growth mode for the past decade in the US, so many low time pilots were hired to fly RJ's that no large aircraft carrier had to use PFT types for his operation. The woods were full of pilots with several thousand hours of jet time, even if it was in the right seat, they made good candidates. If they had some left seat time all the better.
PFT in the US to date has been only applied at the lowest level of the industry, like small turboprop operators. I am not aware of any larger air carrier using this method yet.
Cheers.