Delta Air Lines said Wednesday its pilots had cleared merger plans with Northwest Airlines, removing a possible hurdle of labor disruptions and allowing the companies to create the largest US carrier.

Delta said the Air Line Pilots Association (ALPA) had informed it Wednesday that Delta pilots had overwhelmingly voted to approve a change in their current contract that would promote revenue synergies in the new company.

The ratification vote was more than 3-to-1 in favor, said Lee Moak, chairman of Delta's Air Line Pilots Association chapter.

We are pleased with the Delta pilots' decision to ratify a modification to their current contract, marking an important step towards combining our two great airlines, said Delta chief executive Richard Anderson.

The merger of Delta, the nation's third-largest airline, with number-five Northwest, will create a new mammoth airline that keeps the Delta name and like its namesake, will be headquartered in Atlanta, Georgia.