Chicago O'Hare (ORD): The Complete Layover Guide

O'Hare has four terminals numbered 1, 2, 3 and 5. There is no Terminal 4; the number was retired in the 1990s and never came back. Terminals 1, 2 and 3 form the central horseshoe. Terminal 1 is United's house, with concourses B and C joined by an underground walkway. Terminal 2 holds concourses E and F plus the USO center for military travelers. Terminal 3 belongs to American across concourses G, H, K and L, with three Admirals Clubs and the Flagship Lounge. Terminal 5 sits about a mile east with its single Concourse M, handling most international flights along with Delta.

The core three terminals connect airside. You can walk from a United gate in Terminal 1 to an American gate in Terminal 3 without clearing security again, and that one fact saves more connections here than anything else. The distances are honest hub distances, so a cross complex walk takes real time, but it is all indoors and well signed. On the landside, the free ATS train links all four terminals and the rental car facility. It runs 24 hours a day, comes every few minutes at peak, and completes its loop in about 10 minutes.

Terminal 5 is the complication. No airside walkway reaches it. Between 11:30 am and 9:30 pm an airside Terminal Transfer Bus shuttles connecting passengers roughly every 15 minutes, with stops in Terminals 1, 3 and 5, and you stay inside security the whole way. Outside those hours, your only route is the ATS train on the landside, which means a fresh security line when you arrive. A Terminal 5 connection at 7 am works very differently from one at 2 pm, and your booking engine does not know that.

Security timing is moody. Typical waits run 10 to 25 minutes, but the morning bank from 5 to 8 am and the afternoon push from 4 to 7 pm can stretch lines past 45 minutes. Arriving international passengers clear immigration in Terminal 5, where the average wait sits around 20 to 35 minutes and bad days reach an hour. Global Entry and Mobile Passport Control both operate there and earn their keep.

Connection math, then. Official minimums run as low as about 40 minutes for domestic itineraries, and people make them routinely when both flights use the same terminal. Give yourself 60 to 90 minutes for anything that changes concourses, 2 hours if Terminal 5 is involved, and 2.5 to 3 hours if you are landing from abroad, since you will clear immigration, collect and recheck bags, change terminals and pass security before you see your next gate.

Overnight, the airport stays open and the train keeps running, but the character changes. Most security checkpoints close at night, with Terminal 5 the usual exception, so a late arrival who exits the secure area may not get back in until morning. Gate seating mostly has fixed armrests. The people who sleep here head for the quieter corners of Terminal 3 around concourses H, K and L, the nook near gate C20 in Terminal 1, or simply walk the underground corridor to the Hilton across from Terminal 2 and pay for a bed.

Then there is the construction. O'Hare is deep into a multibillion dollar expansion: Concourse D broke ground in August 2025 with completion targeted for late 2028, a second satellite concourse is planned, and Terminal 2 is eventually due for replacement by a new Global Terminal in the years after that. Expect temporary walls, rerouted walkways and moved bus stops for the rest of the decade. The airport works, but trust the signage over your memory, because the map keeps shifting.