San Francisco International Airport (SFO) Check In

San Francisco International Airport (IATA: SFO) is Northern California’s largest airport and a key hub that links the Bay Area to more than 140 domestic and international destinations. It is a major hub of both United Airlines and Alaska Airlines, and has four terminal buildings: Terminal 1 (Harvey Milk Terminal), Terminal 2, Terminal 3, and the International Terminal, all connected by the free 24-hour AirTrain and walking connectors.

If you’re traveling for the first time or a frequent flyer, knowing what to expect at SFO check-in is the first step to a successful travel day.

Which Terminal is your Airline?

All airlines are in their own terminal at SFO. Before departing for the airport, check the terminal so you can head straight to the right check-in counters and not waste any time going around in circles.

Check-In Options At SFO Airport

There are several options for travelers to check in at SFO, depending on their preferences and schedules. Let’s look at each of these options in action:

1. Online Check-In

Most airlines allow online check-in 24 hours prior to the flight. This is the easiest way to choose and confirm your seat, add luggage and download your mobile boarding pass before you even leave home. United, Delta, American Airlines, and Alaska Airlines are just a few of the major airlines that provide easy online check-in via their website or mobile application. The process of online check-in can help you save a lot of time at the airport and increase your chances of getting your preferred seat.

2. Mobile App Check-In

Most major airlines have strong SFO mobile apps, where you can check in, book seats, get up-to-the-minute flight information and store your boarding pass on your mobile device. The official SFO app does this and more, offering terminal maps, up-to-the-minute gate information, parking updates and estimated security wait times, making it an essential tool for the airport experience.

3. Self-Service Kiosks

Various airlines are operating SFO’s self-service kiosks throughout all terminals. Passengers can check in, print boarding passes and tag their bags without waiting for counter staff at these kiosks. You can check in at a kiosk as late as 45 minutes before your flight, but it’s always better to arrive earlier than that if your airline allows. Kiosks are particularly convenient for travelers who have light bags or no checked bags.

4. Airline Counter Check-In

If you have special needs, require oversized luggage, have a complicated travel plan or need a visa, you should go to the staffed airline counter. Check-in counters are situated at the departures floor of each terminal, and usually start opening three to four hours before the scheduled departure time. Check with your particular airline, as their counter hours may differ.

Pro Tip:

• Baggage drop-off times are typically – 45 minutes before departure for domestic flights 
• Baggage drop-off times are typically – 60–75 minutes before departure for international flights 
• Even if you’re at the airport, you haven’t been checked in until your bags are processed, and you can miss your flight if you arrive just a minute late.

Step-By-Step Check-In Process

Here is the step to step process for you when you want to check in at an airport

Find out what terminal you will be at before you come

Check the airline’s departure terminal and proceed straight to the departures level signage.

Check-in at home via online or app

Lock in your seat and boarding pass 24 hours prior to flight on your airline’s website or app.

Go to the kiosk or counter for bag drop

If you are carrying checked luggage, go to the bag drop counter/kiosk and tag and drop bags.

Present REAL ID compliant ID’s

Effective May 7, 2025, passengers 18 years of age or older will be required to show a driver’s license or other acceptable document to security that complies with the REAL ID Act.

Proceed through security

SFO has six security checkpoints in all its terminals. If you pass through any of the checkpoints, you can walk to any gate in the airport once you are cleared

Expedited Programs Worth Knowing 

At SFO, you can benefit from all the major trusted traveller programmes that can speed up your check-in and security process:

TSA PreCheck: Provides access to special lanes for TSA members to use without removing shoes, laptops, or liquids. Enrollment centers are inside the airport.

CLEAR: Allows you to use biometric verification (fingerprint or iris scan) to verify your identity before you are screened by TSA, bypassing the normal document verification line. All SFO terminals have CLEAR lanes.

Global Entry: U.S. Customs and Border Protection program that provides expedited customs clearance for pre-approved international travelers when they arrive in the United States. The enrollment center is at the International Terminal Pre-Security Arrivals Level, which is open by appointment.

Mobile Passport: Enables eligible incoming international visitors to enter their passport and customs declaration data through an iOS or Android app, and then pass through a fast-track lane.

Checking In for International Flights

The International Terminal is the main check-in area for international passengers at SFO. Give much more time for this — international airlines usually have check-in counters open three to four hours before take-off. You should bring your passport and any necessary visa documents; agents may need to check your documents to issue your boarding pass.

International passengers who arrive at SFO will go through the federal inspection process, then leave the secure area and go through security again before boarding their next flight — unless they were precleared by the U.S. government on their inbound flight. Plan this additional step into your connection time.

Frequently Asked Questions