The American Airlines pilots’ union has a called a strike vote over a threat to impose new contracts.
American Airlines is in Chapter 11 bankruptcy protection in the US and seeking to restructure.
The Allied Pilots Association said it would ballot for a strike if the carrier uses the bankruptcy process to throw out existing agreements.
At the same time, pilots’ leaders met senior executives of US Airways to discuss support for a merger between the carriers.
American is a key business partner of British Airways, while US Airways has a code-share agreement with Virgin Atlantic.
American Airlines said a strike by pilots would be illegal. Courts have previously blocked attempts by airline workers to strike during Chapter 11 proceedings.
The carrier is seeking to cancel pilots’ contracts. A hearing before a federal judge in New York to decide whether it can do so is due on September 4.
A union spokesman said: “Our pilots are looking to resist any move to reject our contract.” However, he said the union continues to want to negotiate and a strike would only go ahead if legal.
Ground staff and cabin crew at American airlines have already accepted new contracts.
The union confirmed a meeting with US Airways chairman and chief executive Doug Parker and other executives took place this week to discuss “the potential for industry consolidation”.
American Airlines has previously dismissed merger overtures from US Airways, arguing it would emerge from bankruptcy protection on its own. But American’s creditors have now pressured it to explore options for a merger.
Willie Walsh, head of BA parent IAG, has indicated he may seek a stake in American.