The union for pilots at United Airlines said new flying procedures set to begin on Friday threaten safety because they haven't had long enough to get used to them.
The union filed court papers asking a judge to delay the new procedures.
Commercial airline pilots precisely follow detailed directions for everything from who talks to air traffic control to who does what when something goes wrong. Pilots from two different airlines might follow different procedures even if they both fly the same kind of plane.
The issue came up at United because it is merging the ranks of United pilots with those who came from Continental.
Wendy Morse, the head of the pilot union at United and a 777 captain, said pilots watched a computer-based slide show that lasts 54 minutes, and that some pilots have been designated to answer questions from fellow aviators. But pilots have gotten no classroom instruction or other training in the new procedures, she said.
Changes include allowing the autopilot to fly the plane out of a severe wind gust rather than flying the plane manually as United pilots currently do, she said.
"I think United pilots will continue to be pretty uncomfortable allowing the autopilot to get out of a wind shear situation when they're close to the ground and about to hit it," she said.
Other changes include the terms that pilots use to update each other and air traffic controllers on their progress toward landing, and whether the captain or the first officer turns off the landing light after landing.
No single change would be difficult, she said, but "there's a whole plethora of changes in a row, and one on top of another, and that is what's creating the angst. Our guys are not comfortable because of a whole list of those kinds of things," she said.
Eighty percent of the procedures that will be used by the combined work group come from Continental, Morse said. Continental pilots, who belong to a separate unit inside the Air Line Pilots Association, were not involved in the court case.
Airline spokeswoman Julie King called the court filing "a shameful effort to influence negotiations for a joint collective bargaining agreement, under a false guise of safety." She said its training procedures are approved and monitored by the Federal Aviation Administration.
Morse said the filing has nothing to do with contract negotiations.
United and Continental pilots still have separate union contracts. They have been negotiating for a joint contract with parent company United Continental Holdings Inc.
The company is aiming to get a single operating certificate from the FAA by the end of the year, and harmonizing flying procedures is one part of that. The two companies merged last year.
Shares of the Chicago-based company rose 97 cents, or 4.7 percent, to close at $21.43 on Monday.