Leaders of the Allied Pilots Association on Wednesday rejected American Airlines' "best and final" offer, meaning rank-and-file pilots will not vote on the proposed contract.
The APA board voted 11-5 to turn down the deal.
"We were very close on many of the items," said APA spokesman Tom Hoban. "Scheduling was the black hole."
Hoban said the company's last offer did not include enough details for the union to vote.
"It was a handful of sheets of paper, and there was far too much ambiguity to understand what we were going to vote on and have the confidence that we could take this to the pilot group and say, 'Yes, you need to vote this up,'" Hoban said.
The rejection came just two days before a bankruptcy judge is set to rule on whether to throw out union contracts and allow the airline to impose new ones.
Hoban said the union would ask the company to request the judge to delay the process.
"With the judge's consent and a little more time, we think we can fix this thing," he said.
The airline issued a statement saying it was "very disappointed" by the APA announcement.
“Both parties worked hard to reach a compromise on what are very intricate and complex issues, resulting in a proposal that provides significant benefits for pilots," said American spokesman Bruce Hicks.
Hicks said the offer included pay increases, furlough protection, profit sharing, and a freeze of the pension instead of termination.
The company statement did not respond directly to the union's request for more time but said the company hoped the union would "ultimately allow our pilots an opportunity to vote."
Flight attendants and two groups of the Transport Workers Union also have not reached a contract agreement with the company.
Asked what would happen if the judge on Friday throws out the current contract, Hoban said the entire process is unclear.
"No pilot group has ever gone through a contract abrogation, so this is a gray zone for us and the industry in general," he said. "But we're hoping we can petition the court with the corporation's help and get an extension on the process and work out the agreement."
Also complicating the process is an effort by US Airways to merge with American Airlines. American's major unions support a takeover by US Airways, saying a larger airline would be more competitive and save more jobs.