Connecting at Houston Bush Intercontinental (IAH): terminals, trains and customs

For a domestic connection on one ticket, an hour is usually enough at IAH if your first flight is on time; for an international arrival it's tight, because you clear customs in Terminal E, collect and recheck your bags and go through TSA security again. Changing terminals takes minutes: a free train inside security leaves every two minutes and takes about 4 minutes 15 seconds from Terminal A to Terminals D and E. The airport doesn't publish a minimum connection time.

Is 1 hour enough at IAH?

For a domestic connection on one ticket, often yes. The airline only sells connections that meet its own minimum for Houston, and if you miss the second flight because the first was late, it has to rebook you. The ride between terminals is short, so what matters is how late your first flight lands and how far your next gate is from the train.

For an international arrival connecting to a US flight, an hour is tight. The airport doesn't give a time for passport control, collecting bags, rechecking them and the security line, and each of those can take a while at busy hours (see the customs wait times below).

If you booked the two flights separately, nobody checks that your layover is long enough and the second airline doesn't have to wait. Leave far more than an hour. Read is a 1-hour layover enough?

Are the terminals connected? Can you stay inside security?

Yes. IAH has five terminals, A to E, and two free trains link them:

• The above-ground train runs inside security. This is the one for connections. Stations are in Terminal A, Terminal C and Terminals D/E, which share a station.
• The underground train runs outside security, every three minutes from 3:15 a.m. to 12:15 a.m. It's for people who haven't been through security yet. If you ride it on a connection, you have to go through a TSA checkpoint again.

The airport doesn't publish walking routes or walking times between terminals. The airport's advice: if you're already through security, take the train inside security.

Changing terminals at IAH

Add the walk from your gate to the station and from the station to your next gate. Check your gate on your boarding pass or the airline's app before you land, because gates can change during construction.

Arriving from another country (international to domestic)

International flights arrive at gates in Terminal D or E. From there, the airport's steps are:

1. Walk to the inspection area through secure corridors and sky bridges.
2. Clear passport control in the immigration hall in Terminal E, with an officer or, if you're a member, at a Global Entry kiosk.
3. Collect your checked bags on level one, even if they're tagged to your final city.
4. Clear customs at the exit control.
5. Turn right after customs to the recheck counters and drop your bags for your next flight.
6. Go through TSA security before you enter the secure area of the terminal your next flight leaves from, then take the train if you need another terminal.

IAH takes part in CBP's Mobile Passport Control, which gives eligible travelers (US citizens, US permanent residents, Canadian visitors and returning Visa Waiver Program travelers with an approved ESTA) a dedicated line at passport control. Read international to domestic connections.

Domestic to international

If you arrive on a domestic flight and leave on an international one from Terminal D or E, you stay inside security and take the train to D/E. On one ticket your bags should be checked through, but ask at check-in if you're unsure. On separate tickets you have to leave security, collect your bags, check in for the second flight and go through security again.

Since March 2026 several international airlines check in at Terminal E instead of Terminal D, so if you're starting from outside security, confirm your check-in terminal with your airline. Terminal E has a 17-lane TSA checkpoint with TSA PreCheck.

What's changing at IAH in 2026 and 2027

• Terminal B North opened on October 22, 2026, a new 22-gate concourse for United. Until the new Terminal B lobby opens in a later phase, you check in, clear security and reach the B North gates through the Terminal C departures lobby.
• Terminal B South is next in the same rebuild. The airport hasn't given a date.
• International check-in has been moving to Terminal E in phases since March 3, 2026.

We'll check these again in February 2027. Until then, trust your boarding pass and the signs at the airport over any map you saved earlier.

Customs wait times

From October 2025 to September 2026, passengers arriving from abroad at IAH waited 20 minutes on average to clear passport control, according to CBP: 15 minutes for US citizens and 27 minutes for visitors. 4.2% waited more than an hour. The slowest arrival hour was 5 a.m.–6 a.m., averaging 23 minutes. These times don't include collecting bags or walking to your next gate. See US customs wait times by airport.

On-time record

From September 2025 to August 2026, 79.9% of scheduled arrivals at Houston (IAH) reached the gate on time, rank 4 of the 30 busiest US airports. 78.5% of departures left on time and 1.1% of departures were canceled. The largest share of delay minutes came from late-arriving aircraft. See the full US airport on-time ranking.

Follow the first flight

Add both flights to FlyingOver before you travel. You'll follow the first flight offline and see its estimated arrival, and with Premium, connection guidance shows whether your layover looks comfortable, whether you need to keep moving or whether you should go directly to the gate.