While American Airlines is duking it out with online booking services like Expedia and Orbitz, US Airways recently announced a multi-year strategic partnership agreement to continue offering US Airways’ “full range of products and services, including all fares and inventory, through Expedia, Hotwire and Egencia sites around the world,” according to a press release from US Airways.

Expedia will also work with US Airways to enable customers to purchase window or aisle seats through channels such as the Expedia online travel marketplace.

US Airways’ Senior Vice President, Marketing and Planning, Andrew Nocella said, “We are committed to making it as easy as possible for our customers to purchase tickets from US Airways through as many sources as possible.”

Bottom line: Because airlines are increasingly offering more on their sites than just an airline seat (paying extra for bonus miles, lounge access, preferred seating and more), they are even more reluctant than in the past to let their customers book through third-party sites. US Airways is going another route by working with a third-party site to offer more than just seats.

The Wall Street Journal recently reported that Delta, like American Airlines, wants their customers coming directly to them, “We look at it very much like an Apple store versus Best Buy,” said Glen Hauenstein, Delta’s head of revenue management.