New York - Pilots at Delta and Northwest agreed Tuesday to a tentative joint contract that could clear the way for a merger of the airlines, the companies said in a statement.

Without such a deal - which irons out seniority issues among the flight crews allowing them to determine issues such as pay, flight routes and which airplanes pilots are allowed to fly - the merger was unlikely to take place.

Delta, the third-largest US airline, and number five Northwest Airlines announced their merger in April, which would make the joint firm the world's largest by passenger volume. (dpa)