Some of these routes were sustainable at $70 oil; some even at $80, but given the way things are with no sign of a let-up (frankly IMO, the USD will continue to fall this year which will contribute to oil prices being up there), a lot of these routes simply cannot be sustained.

As for mainline aircraft to be parked, look for the MD88s, 757s, and even domestic 763s to be grounded before any 737s.