Do I go through security again for a connecting flight?

It depends on whether you stay in the secure area. For most domestic-to-domestic connections on the same airline, you stay airside (past security) and walk or take a shuttle to your next gate — no second screening.

You WILL go through security again if: you leave the secure area (to pick up checked bags, go to a different terminal without an airside connection, or leave the airport during a long layover). At airports like JFK, where each terminal is essentially separate, changing from Terminal 1 to Terminal 4 means exiting security and re-screening. At ORD, Terminals 1-3 are connected airside, but the international Terminal 5 requires re-screening.

International-to-domestic connections always require going through customs and immigration first, rechecking bags, then going through TSA security again. This is true at every U.S. airport and is why international connections need extra time — typically 2-3 hours minimum at busy ports of entry like MIA, JFK, or LAX.