However, the airline industry is both capital and labor intensive. Also, most employees at Southwest Airlines are unionized, depending on various U.S. labor organizations. Failure to amend terms and conditions suitably with these unions may lead to work stoppages or strikes and hamper operations. Furthermore, the charged levied by the U.S. Transportation Department against five major American carriers including Southwest Airlines and its rivals, Delta Air Lines Inc. DAL, United Continental Holdings Inc. UAL and American Airlines Group Inc. AAL is a major concern.