PSA and Northwest OKd a marketing agreement.

Pacific Southwest Airlines will integrate its flight schedule with Northwest’s in an effort to pick up additional travelers, PSA said. It is the third sizable carrier to reach such an agreement this month. Previously, Western Airlines and Delta Air Lines announced similar pacts with Japan Air Lines, and both said they expect revenue boosts. The link-up with PSA would give Northwest the ability to route travelers straight through to destinations served by PSA.