Labor uncertainty is threatening the future of regional airline Comair, its president said Monday as the Delta subsidiary sought bankruptcy court permission to void its contract with flight attendants.

Comair Inc. and its flight attendants have been negotiating for more than six months over the last unresolved contract among the bankrupt airline’s unions. Pilots and mechanics had reached agreements, but the company said those deals — which cannot take effect until all unions reach a new agreement — may now need to be renegotiated. Those deals were contingent on an overall restructuring plan.