United, Delta to Merge Mileage Plans in Sept.

UAL Corp.’s United Airlines and Delta Air Lines Inc. said they will merge their domestic frequent-flier plans Sept. 1, the first step in a larger proposed alliance between the carriers. The plan would allow passengers on either airline to earn frequent-flier miles in the other’s program on flights in the United States and Puerto Rico and the U.S. Virgin Islands. It is part of a proposed alliance that would also include code-sharing, which allows for near-seamless travel on trips that involve a transfer between the airlines. Code-sharing would require approval from both Delta’s and United’s pilots unions under current labor agreements. Merging frequent-flier programs does not require the approval, but Chicago-based United said last week that the pilots would be consulted on that move as well.