United Airlines and US Airways continue to negotiate a possible merger and could reach an agreement within the next 10 days, according to media reports. Talks have been ongoing for about six weeks, and the airlines have identified about $1.5 billion in potential cost savings. United is also considering a transaction with Continental Airlines, reports say. Observers say integrating workforces remains a concern for the carriers. They say United and US Airways would want their transaction to receive antitrust scrutiny on the same schedules as the anticipated merger of Delta Air Lines and Northwest Airlines.