Battles over union seniority lists for pilots are becoming huge obstacles to recent airline mergers. A dispute between pilots at US Airways and America West has led to notable unrest in the wake of the airlines' merger, and similar tensions are delaying merger talks between Delta Air Lines and Northwest Airlines.
See "Pilots? Battles Over Seniority Play Havoc With Airline Mergers", Jeff Bailey, The New York Times, February 26, 2008