UAL ( UALAQ), parent of United Airlines, may have another hurdle to clear in its long-running efforts to emerge from bankruptcy protection.

Members of the airline's machinists union have reportedly rejected a proposal to cut salaries and benefits. The mechanics union, the Aircraft Mechanics Fraternal Association, said members also approved a strike.

UAL has been operating under Chapter 11 bankruptcy protection for more than two years now and is working hard to cut costs under difficult circumstances.

UAL has set a target of $2 billion in savings from labor, nonlabor and pension costs on top of the $5 billion in average annual savings it had previously announced.

The Chicago-based carrier posted a net loss of $664 million, or $5.73, including items, compared with $476 million, or $4.33 a share, in the year-ago period. Excluding items, UAL lost $553 million, or $4.77 a share, vs. $252 million, or $2.30 a share, a year ago. Operating revenue, however, rose 5% to $4.0 billion.