The Red Line is the name given to the service along the first branch off or the original East-West (now Blue Line alignment), the Airport MAX opened as a 5.5 mile extension on September 10, 2001. This extension originally saw service between the Airport Downtown and the Library and Galleria Stations (turning around on the loop tracks). On September 1, 2003, service was extended the Beaverton Transit Center to bring Red Line service farther west and provide one-seat ride service between the Airport and this important destination. Trains were originally single LRVs but in 2005, they were expanded to be two LRVs long with the Yellow Line (who’s ridership wasn’t meeting expectations) becoming a single LRV car to reduce crowding by passengers to and from the Airport.

The original Red Line extension was built on the cheap with two single track sections, one is a loop of track where Red Line trains make a loop and cross under the main Blue Line tracks after leaving Gateway Transit Center, and another single-track section entering the airport.

As part of a way to bring more reliable service to the Red Line and the entire MAX A Better Red project ran from 2021 through 2024, and consisted of double-tracking the formerly single-tracked sections of the Red Line. This project included the building of a new station Gateway North for westbound trains (see that page for more information) and rebuilding the Airport MAX station. Starting in August 2024 all Red Line trains will be extended to Fair Complex/Hillsboro Airport, supplementing Blue line trains at all stops to provide better service along this important section of train line. This extension project made the Red Line double-tracking project a proper expansion project allowing it to qualify for additional Federal Funding programs.