[5] The City of Chicago first awarded the contract for the people mover system to Westinghouse Electric, the second lowest bidder, in 1985.

The expansion included replacing the existing 15-car fleet with 36 new Bombardier Innovia APM 256 vehicles, upgrading the previous infrastructure, and extending the line 2,000 feet (610 m) to the new Multi-Modal Facility on the east side of U.S. 12–45 (Mannheim Road).

[2][11][12] Originally, the ATS was to reopen by Fall of 2019, but this was delayed several times due in part to the COVID-19 pandemic, contract disputes, and reliability.

[13] The system is free to users and connects O'Hare's terminals to parking lots, and the consolidated rental car facility.

[15] The ATS originally used the French-based VAL technology, which features fully automated, rubber-tired people mover cars that previously saw use on the Jacksonville Skyway until 1989.

The system is capable of traveling at speeds of up to 50 mph (80 km/h), and now uses 12 3-car Bombardier Innovia APM 256 trains, which replaced the previous 15 Matra VAL 256 vehicles.

[16] As of 2023, the previous 15 VAL trains are sitting in a vacant lot on airport property near Irving Park Road and Taft Avenue.