The biggest question is what can you replace the tri with that's any where near costs effective.
Anything that pressurised gets murdered on cycles between the Islands.
Same with the engines if they are turbines.
I presume the capital hit per start and sector is spread over an ATR's worth of punters. Anything smaller and the ticket price would cause outrage.
Anything that shouts it might be ok to use is dead eg Shorts 360.