United Airlines unions say they have spent several years preparing for a potential merger with another airline.

No merger has been publicly announced, but the most recent of many rumors involving United has the Chicago-based airline as a possible merger partner for Continental Airlines or Delta Air Lines.

"We've been preparing for a potential merger since late 2004," said Sara Nelson Dela Cruz, spokeswoman for the Association of Flight Attendants at United.

Her union is hopeful that a merger could bring more jobs or an opportunity to negotiate better pay and benefits.

"The industry is headed towards consolidation to expand," Dela Cruz said. "That is a sign of good things for the airline industry, and the employees who have sacrificed so hard to keep the industry afloat stand to benefit from profits or any industry turnaround."

The Air Line Pilots Association at United has a merger committee that meets regularly and has been preparing a review of issues pilots would face in a consolidation scenario.