Originally Posted by
wrp96
As long as you have a same day boarding pass for that airport, you can clear security at any terminal at ORD. Even better though is March 1st, the airside buses start back up so you'll be able to go from T5 to T1-T3 and vice versa without having to leave security.
While some TSA agents will have issue, technically you can clear into any terminal regardless of if airline can be accessed from it. TSA made this clear a few years ago. However like anything TSA related, it's a ****shoot if agents knows that.
Also, FYI same is true at CDG with 2E K, L, and M access. Although they do try and stop you, they started allowing, especially since food is basically all airside in 2E once past immigration.