IF Mesa were to go into BK...
Delta would take advantage of their ability to void the contract.
Without the income afforded by the DL contract, Mesa will not be able to secure exit financing.
Mesa aircraft will be sold to raise capital to cover debts.
The CRJ 900 aircraft will be sold, as they have the highest value in the current market.
Look for the Freedom CRJ 900 aircraft to end up at Mesaba or Pinnacle.
Look for the US Airways CRJ 900's to end up over with mother Delta too. This, however, might be a more complicated transaction.
The US Airways CRJ 900 flying will be replaced by another carrier, and not become a capacity reduction. Republic and Skywest will be the two final suitors. Perhaps Republic will try to accquire the Compass 175's, in exchange for the Mesa CRJ 900's in Airways paint. This would give Airways more Embraers and more commonality in product, and it would give Delta a similar benefit, as they favor the CRJ 900.
United will jump on the bandwagon and end at least part of its Mesa contract. Look for Skywest to gain the CRj 700 flying and aircraft. Mesa will continue to operate some of its CRj 200 aircraft for United under a modified contract.
Comair or ASA will end up with the leftover CRJ 200's from United's Mesa flying. These aircraft will be flown for Delta in place of the missing 50 seat Embraer capacity, though probably at a ratio of 1 "new" CRJ for every 2 145's removed from the DCI fleet.
The biggest question is what comes of the Mesa Dash 8's... They serve a necessary role overall, so somewone will pick them up. Perhaps Great Lakes will pick up a new fleet type, or Commutair will get a whole new arena to play in. Unfortunately, i think Piedmont will balk at the opportunity (foolishly).
Mesa will exit bankruptcy at about 1/4 to 1/3 of its original size, with a fleet of CRJ 200's being flown for United under a relatively stable contract.
In 4 years, all of the above mentioned mainline partners will completely forget about what happened, and award new aircraft and flying to Mesa, thus beginning the cycle anew.