The boards of directors of Delta Air Lines and NorthwestAirlines were expected to vote Wednesday on a combination provided their pilot unions can reach their own integration deal by then, people briefed on the discussions said Tuesday.

If the pilot agreement can't be reached by the time of the meeting, the boards were expected to just get an update on the status of merger talks between the two airlines, according to three people familiar with the situation who asked not to be named because the talks were in a sensitive stage.