Originally Posted by OSSYULYYZ

Unless preclearance gets revoked. Preclearance only clears you to land at that specific airport w/o going through customs apparently...not entry to the US officially... This happened in YYZ in 2015:

I was in the preclearance zone in the old terminal 2 commuter flight area, and a couple had just missed their flights. They were rescheduled to fly in 90 min. The Air Canada GA agent told them that they MUST leave the preclearance area because they were only cleared to land at CLE and not that the location they were rerouted to. From my understanding, they had to clear CBSA and then re-clear CBP Preclearance. Maybe rules have changed since then

Originally Posted by EmailKid

Pretty sure that rules did NOT change, this was a misinformed agent @:-)

Allow me to present FIRST HAND experience, i.e. myself.

At YVR gate (probably 88 or thereabout) and ask to do SDC to maximize EQMs.

Agent: "That will be $50."

Um, no UA gold, SDC is free and agent immediately acknowledged that.

"Here you go, here is your new boarding pass."

No exiting and reentering to land at a completely different city - LAX instead of DEN IIRC. About two, maybe three years ago.