Flight attendants at Northwest Airlines Corp. have voted to reject a concession package, setting up possible work stoppages that could cripple the airline’s restructuring.

The Association of Flight Attendants-CWA said late Monday that the tentative agreement it negotiated with the airline had been rejected by a margin of 3,266 to 2,637. It’s the second time flight attendants at the company had voted down a deal negotiated by their union.