ATLANTA — Leaders of Delta Air Lines Inc.'s pilots union were meeting in special session, the union said yesterday as the company was trying to determine whether to move forward on a merger with Northwest Airlines Corp.

Union spokeswoman Kelly Regus said in a memo to rank-and-file Delta pilots that the Master Executive Council meeting was taking place in Atlanta.

She did not say how long the meeting would last or what was being discussed.

Northwest pilots union leaders are scheduled to meet tomorrow in Bloomington, Minn., to discuss merger issues.

People familiar with the discussions between Delta and Northwest said earlier this week that Delta is deciding whether to push ahead with a merger with Northwest without a prearranged deal between their pilots — a move that could change details of the deal.

Delta and Northwest are looking at their route structures and how a combination now would affect them, given $110-a-barrel oil and a decision by both carriers to cut domestic capacity, one of the sources said.

Another source said there is no particular timeline or deadline for the airlines to decide whether to proceed with a deal, and things could still fall apart.