I have T-Mobile and get great coverage at the airport but generally poor coverage once in the plane.
My theory is that the Atlanta airport has one or more
DAS (Distribuited Antenna System) within the building(s) that makeup the terminals and concourses. That gets me the great coverage while in the airport.
When I am in the plane I am relying on the cellular towers outside which may be a considerable distance from me somewhere off the airport grounds while also being inside a tin can which blocks the signal.
So my ultimate guess is that the DAS system is only using 4G technology for at&t.
After typing this I gave it a Google and got the following:
Yes, Hartsfield-Jackson Atlanta International Airport (ATL) has a
Distributed Antenna System (DAS) that provides cellular coverage throughout its facilities.
Key details regarding the system include:
- Coverage: The DAS covers the terminal, atrium, all six concourses, and the underground transportation mall.
- Neutral Host: The system is a "neutral host" network, meaning it supports multiple major cellular carriers rather than just one.
- Upgrade Project (2025-2026): As of mid-2025, the airport began a major upgrade of this system to replace older equipment with new infrastructure to support 5G capabilities, with full integration expected to improve data performance in the terminals.
- Public Safety: In addition to public cell service, the system includes a separate, dedicated layer to support airport operations and public safety communications.
While a DAS exists, travelers have historically experienced variable service quality in certain areas—such as high-ceiling concourses—which is being addressed by the 2025/2026 upgrade project.