San Francisco SFO Airport Terminal Transfer Guide: International Terminal to T1, T2, T3 AirTrain, Walkways, MCT, and Baggage Rules (2026)

Quick Summary

• Primary Update: San Francisco International Airport (SFO) features an automated 24/7 AirTrain people mover network alongside post-security airside connector walkways linking Harvey Milk Terminal 1, Terminal 2, Terminal 3, and International Terminal Boarding Area G, enabling seamless domestic transfers without re-screening.
• Transit Impact: All arriving international passengers must clear U.S. Customs and Border Protection (CBP) passport control, claim all checked baggage, and hand luggage to airline re-check belts before taking the escalator up to TSA screening checkpoints for onward domestic connections; sterile international-to-international transit does not exist in the United States.
• Traveler Advice: Single-ticket domestic-to-international transfers require a minimum of 60 to 75 minutes; international-to-domestic transfers require at least 90 to 120 minutes (2 hours strongly recommended during midday transpacific arrival banks). Separate-ticket self-transfers require a minimum buffer of 3.5 to 4 hours.

San Francisco International Airport (SFO) serves as the primary transpacific and transatlantic aviation gateway for Northern California and the premier West Coast hub for Star Alliance and United Airlines. Handling over 50 million annual passengers across four passenger terminals, SFO facilitates high-frequency connections between long-haul flights from India, Asia, Europe, and Oceania, and hundreds of domestic routes across the United States.

Transferring between terminals at SFO involves two distinct systems: an automated people mover system (AirTrain) operating on the landside pre-security level, and an extensive network of airside connector walkways that permit passengers to walk between select terminals without leaving the secure zone. However, federal border control rules govern all arriving international fliers, dictating mandatory baggage retrieval and security screening before entering departure concourses.

            NORTH / EAST WING                                                SOUTH / WEST WING
  [ International Terminal A ]                                      [ International Terminal G ]
  Non-Alliance & SkyTeam / oneworld                                 Star Alliance & United International
  (Gates A1-A15)                                                    (Gates G1-G14)
        ^                                                                 ^
        | Airside Connector                                               | Airside Connector Bridge (3-5 min walk)
        v                                                                 v
  [ Harvey Milk Terminal 1 ] <--- Airside Walkway ---> [ Terminal 2 ] <--- Airside Walkway ---> [ Terminal 3 ]
  Gates B1-B27, C1-C11                                 Gates D1-D18                             Gates E1-E13, F1-F22
  American, Southwest, JetBlue                         Alaska, Delta                            United Airlines Domestic

=======================================================================================================================
                    LANDSIDE 24/7 AIRTRAIN AUTOMATED PEOPLE MOVER (FREE ELEVATED TRAIN)
  RED LINE:   Int'l Terminal A <-> T1 <-> T2 <-> T3 <-> Int'l Terminal G / BART <-> Garages (Terminal Loop)
  BLUE LINE:  All Terminals & Garages + West Field Garage + Grand Hyatt Hotel + Rental Car Center + Long-Term Parking

Terminal Layout and Airline Distribution

SFO is structured around a central circular roadway. The campus is divided into four main passenger complexes: the International Terminal (subdivided into Boarding Area A and Boarding Area G), Harvey Milk Terminal 1, Terminal 2, and Terminal 3.

International Terminal: Boarding Areas A and G

The International Terminal features a central Main Hall with ticketing on Level 3, arrivals and baggage claim on Level 2, and ground transport on Level 1. Departures branch into two separate, secure boarding wings:

• Boarding Area A (Gates A1–A15): Houses non-Star Alliance international carriers and select SkyTeam and oneworld members. Major operators include Emirates, Qatar Airways, British Airways, Virgin Atlantic, Air France, KLM, Cathay Pacific, Japan Airlines, Korean Air, Philippine Airlines, Qantas, Fiji Airways, Aer Lingus, and Iberia.
• Boarding Area G (Gates G1–G14): Houses Star Alliance international carriers and United Airlines long-haul international flights. Key operators include Air India (nonstop services to Delhi, Mumbai, and Bengaluru), United Airlines International, Singapore Airlines, All Nippon Airways (ANA), EVA Air, Lufthansa, Swiss International Air Lines, TAP Air Portugal, Air New Zealand, Turkish Airlines, Asiana Airlines, and Copa Airlines.

Harvey Milk Terminal 1 (Gates B1–B27 and C1–C11)

Named in honor of the civil rights pioneer, Harvey Milk Terminal 1 is a newly modernized concourse serving American Airlines, JetBlue, and Southwest Airlines, alongside select shared regional operations. It features high-capacity security screening lanes and dedicated post-security connectors to both Terminal 2 and International Boarding Area A.

Terminal 2 (Gates D1–D18)

Terminal 2 serves as the primary base for Alaska Airlines and Delta Air Lines. The terminal includes full baggage claim facilities on the ground level, dedicated TSA PreCheck and CLEAR lanes, and continuous post-security walkways linking east to Terminal 1 and west to Terminal 3.

Terminal 3 (Gates E1–E13 and F1–F22)

Terminal 3 is United Airlines' primary domestic mega-hub at SFO. Divided into Concourse E and Concourse F, it handles hundreds of daily departures across North America. Terminal 3 connects directly to International Boarding Area G via an airside connector bridge, allowing Star Alliance passengers to switch between domestic and international flights in under seven minutes.

SFO AirTrain: Red Line vs. Blue Line

The SFO AirTrain is a fully automated, driverless elevated people mover system operating 24 hours a day, 365 days a year. AirTrain stations are located on Level 4 of all domestic terminals and on Level 4 of the International Terminal Main Hall. Riding the AirTrain is completely free.

Feature                     | Red Line                                      | Blue Line

Service Route               | Terminal Loop Only                            | Full Campus & Remote Facilities
Stations Served             | Int'l A, T1, T2, T3, Int'l G / BART, Garages  | All Terminals + Grand Hyatt + Rental Cars
Frequency                   | Every 3 to 5 minutes                          | Every 3 to 5 minutes
Operating Hours             | 24 hours daily, 365 days a year               | 24 hours daily, 365 days a year
Fare                        | Free (No ticket required)                     | Free (No ticket required)
Security Status             | Landside (Pre-security only)                  | Landside (Pre-security only)
Recommended Use Case        | Rapid transfer between passenger terminals    | Rental cars, long-term parking, Hyatt

Travelers must pay close attention to platform signage:

1. Red Line: Operates strictly within the passenger terminal loop. It provides the quickest transit between domestic terminals, International Terminal A, International Terminal G, and the BART rail station.
2. Blue Line: Follows the identical passenger terminal loop as the Red Line, but continues along an extended northern track to serve the SFO Grand Hyatt Hotel, the West Field Garage, the consolidated Rental Car Center, and Long-Term Parking.

If transferring between terminals, boarding either a Red Line or Blue Line train will carry you to your destination. However, passengers returning to the terminals from the Rental Car Center or Long-Term Parking must board the Blue Line, as the Red Line does not serve remote facilities.

Airside Connectors vs. Landside Transfers

SFO provides two distinct methods for moving between gates: walking through the post-security airside connector network or riding the landside AirTrain.

The Airside Walkway Loop (Post-Security)

SFO features an interconnected post-security walkway network that connects Harvey Milk Terminal 1, Terminal 2, Terminal 3, and International Terminal Boarding Area G. Passengers already inside the secure area can walk between these facilities without exiting through security checkpoints or presenting boarding passes to TSA agents again:

• Terminal 3 to International Concourse G: Connected via a wide, glass-enclosed airside bridge. The walk takes 3 to 6 minutes.
• Terminal 2 to Terminal 3: A post-security pedestrian corridor linking Gates D and E. Walking time is 5 to 8 minutes.
• Terminal 1 to Terminal 2: A secure connector walkway linking Concourse C and Concourse D. Walking time is 6 to 9 minutes.
• Terminal 1 to International Concourse A: Connected via a dedicated airside connector. Walking time is 4 to 7 minutes.

Because International Boarding Area A and International Boarding Area G are physically separated by the International Terminal ticketing hall, there is no direct airside link between Concourse A and Concourse G. Passengers transferring between international carriers across these two boarding areas must exit the secure area, walk through the public Main Hall (or take AirTrain), and clear TSA security at the other concourse checkpoint.

Minimum Connection Times (MCT) and Operational Rules

Minimum Connection Times at SFO vary significantly based on whether the arriving sector is domestic or international, and whether checked luggage must be re-processed through federal inspection.

International Arrival and U.S. Customs Protocols

The United States does not provide sterile international transit. Every passenger arriving at SFO from an international origin—even those departing on a connecting flight to Canada, Mexico, Europe, or Asia—must be formally processed through U.S. border control.

1. DEPLANE AIRCRAFT          --> Follow overhead "Arrivals / Connections" directional signs into sterile corridors

2. U.S. PASSPORT CONTROL     --> Enter Federal Inspection Services (FIS) Hall at Boarding Area A or G
                                 Lines: U.S. Citizens / LPR, Global Entry, Mobile Passport Control (MPC), Foreign Vistors

3. MANDATORY BAGGAGE CLAIM   --> Collect ALL checked bags from international baggage carousels in customs hall
                                 (Even if bag tags indicate final destination like ORD, DFW, JFK, or SEA)

4. U.S. CUSTOMS CLEARANCE    --> Pass customs exit inspection point with declaration forms / biometric confirmation

5. CONNECTING BAGGAGE DROP   --> Place luggage directly onto airline re-check belts immediately outside customs doors
                                 United Transfer Desk (Int'l G exit) or Multi-Airline Re-Check Counters (Int'l A exit)

6. PROCEED TO DEPARTURES     --> Take escalators up to Level 3 Departures Hall
                                 Walk airside or ride AirTrain to connecting domestic terminal

7. TSA SECURITY SCREENING    --> Clear full TSA security screening at domestic terminal checkpoint

Mandatory Luggage Retrieval and Re-Check Rules

A frequent point of confusion for arriving international passengers is checked baggage. Even when luggage tags display the airport code of your ultimate destination (such as Chicago O'Hare, Dallas/Fort Worth, or Denver), federal statutory regulations require all checked baggage to be retrieved at the first port of entry into the United States.

1. Customs Baggage Hall: After passing passport control kiosks, you must proceed to the assigned carousel and collect every checked suitcase, box, and stroller.
2. Customs Exit: Walk past the CBP agricultural inspection desks with your luggage.
3. Dedicated Re-Check Belts: Directly outside the customs exit doors, dedicated airline re-check desks operate:
   • At International Terminal G, United Airlines maintains a fully staffed transfer facility with baggage drop belts and customer service counters capable of rebooking missed connections or printing onward boarding passes.
   • At International Terminal A, a multi-carrier baggage transfer desk accepts bags tagged for connecting flights on Delta, American, Alaska, and partner carriers.
4. If your bags are already tagged through to your final destination, an agent scans the bag tag and places it onto the conveyor system. You do not need to pay additional baggage fees.
5. If you are traveling on separate tickets and your bags were only checked to SFO, you cannot use the transfer drop belt. You must carry your luggage out to the public arrivals lobby, take the elevator up to Level 3 Departures or ride the AirTrain to your onward airline's terminal, and check in at the public ticketing counters before the baggage cut-off deadline (usually 45 to 60 minutes before domestic departure).

Traveler Logistics Guide

Navigating SFO efficiently requires selecting the correct transfer pathway based on your arrival gate and connection type.

Step-by-Step Directions: United International (G) to United Domestic (T3)

The connection between an inbound international flight arriving at Boarding Area G and a domestic United departure at Terminal 3 represents the highest-volume transfer itinerary at SFO:

1. Deplane at Boarding Area G and follow the secure elevated ramps directly down into the Federal Inspection Services (FIS) facility.
2. Complete U.S. passport control at the CBP inspection booths. If you are eligible for Mobile Passport Control (MPC), submit your details via the authorized CBP smartphone app prior to landing to access dedicated expedited lanes.
3. Retrieve all checked luggage from the assigned carousel in the International G customs hall.
4. Clear the CBP customs exit doors and immediately approach the United Connecting Baggage Desk located directly on your left. Hand your bags to the ground agents.
5. Exit into the public International Arrivals Hall (Level 2). Follow the overhead signs for "Terminal 3 / Domestic Flights."
6. Take the adjacent escalator up to Level 3 (Departures).
7. Walk across the short indoor connecting corridor directly into the entrance of Terminal 3.
8. Enter the TSA security screening checkpoint at Terminal 3 (Security Checkpoint F or E). If enrolled in TSA PreCheck or CLEAR, proceed to the dedicated expedited lanes.
9. After passing screening, check flight information display screens for your gate assignment (Gates E1–E13 or F1–F22). Total transit time from customs exit to domestic gate is typically 15 to 25 minutes.

Step-by-Step Directions: Air India (Int'l G) to American or Alaska Airlines (T1 or T2)

For passengers arriving on Air India flights (AI173, AI179, or AI175) connecting onward to American Airlines (Terminal 1) or Alaska Airlines (Terminal 2):

1. Clear CBP passport control and retrieve your checked bags in the International G customs hall.
2. If your luggage is through-tagged to your domestic airline, hand it to the transfer desk staff. If your itinerary involves separate tickets, retain your luggage.
3. Exit into the public International Arrivals Hall and take the escalator or elevator up to Level 4 to reach the AirTrain Station (International Terminal G).
4. Board the Red Line AirTrain (or Blue Line) departing toward the domestic terminals.
5. Disembark at Terminal 1 Station (for American Airlines) or Terminal 2 Station (for Alaska Airlines). The AirTrain ride takes approximately 3 to 5 minutes.
6. Take the escalator down to Level 3 Departures. If you still have luggage, check in at the airline counter.
7. Clear TSA security at the Terminal 1 or Terminal 2 checkpoint and proceed to your departure gate. Allow at least 25 to 35 minutes for this transfer following customs clearance.

Connecting Outbound: Domestic (T1, T2, or T3) to International Concourse G

If you are flying from an interior U.S. city to SFO to board a long-haul international flight departing from Boarding Area G:

1. Deplane at your domestic gate in Terminal 1, 2, or 3.
2. Do not exit through the security exit doors toward baggage claim.
3. Look for overhead signage indicating "Gates G / International Terminal."
4. Follow the post-security airside connector walkways:
   • From Terminal 1: Walk through the connector into Terminal 2, proceed through the connector into Terminal 3, and follow the signs across the airside bridge into International Concourse G (total walking time: 16 to 22 minutes).
   • From Terminal 2: Walk through the connector into Terminal 3, then proceed across the bridge to International G (total walking time: 10 to 14 minutes).
   • From Terminal 3: Walk straight across the connector bridge adjacent to Gate F1 into International Concourse G (total walking time: 3 to 6 minutes).
5. Arrive directly at your international departure gate without clearing security or showing documents until boarding gate checks.

Public Transit and Hotel Connections

• BART Station Access: The Bay Area Rapid Transit (BART) station is situated on Level 3 of the International Terminal Main Hall, directly on the Boarding Area G side. Passengers arriving at domestic terminals can take the AirTrain Red Line directly to the "Garage G / BART" station stop. BART trains provide direct service to downtown San Francisco (Market Street, Powell, Montgomery) in 30 minutes, and cross-bay service to Oakland and Berkeley.
• SFO Grand Hyatt Access: Travelers with overnight layovers can access the 351-room SFO Grand Hyatt without walking along vehicle roadways. Board the AirTrain Blue Line from any terminal station and disembark at the dedicated "Grand Hyatt SFO" station, which features direct indoor bridge access to the hotel lobby.

Frequently Asked Questions

Can I walk between terminals at SFO without going through TSA security again?

Yes, provided you are traveling within the domestic terminals and International Boarding Area G. SFO features an unbroken post-security airside walkway connecting Harvey Milk Terminal 1, Terminal 2, Terminal 3, and International Concourse G. You can walk freely between these concourses without exiting through security checkpoints. However, International Boarding Area A is physically separated from Concourse G landside; transferring between Concourse A and Concourse G requires exiting security and re-clearing TSA at the other boarding area.

Do I have to collect my luggage at SFO if I am connecting from an international flight to a domestic flight?

Yes. Under U.S. federal customs regulations, all passengers arriving from a foreign airport must retrieve every piece of checked luggage from the international carousel inside the customs hall, regardless of whether the baggage tag lists a final domestic destination. After clearing customs, passengers traveling on a single ticket immediately place their luggage onto dedicated airline re-check belts located directly outside the customs inspection area before proceeding to TSA screening for their domestic flight.

What is the difference between the SFO AirTrain Red Line and Blue Line?

The Red Line is an inner terminal loop that operates strictly between passenger terminals (International A, Terminal 1, Terminal 2, Terminal 3, International G), the terminal parking garages, and the BART rail station. The Blue Line serves all the same passenger terminals and garages as the Red Line, but also travels outward to remote facilities, including the SFO Grand Hyatt Hotel, the West Field Garage, the consolidated Rental Car Center, and Long-Term Parking. Both lines are free and operate 24 hours daily.

How much connection time do I need between an Air India flight and a domestic United flight at SFO?

A minimum connection time of 90 to 120 minutes is recommended. While the physical walk from the customs exit at International Terminal G into Terminal 3 takes less than 5 minutes, you must account for passport control queues, baggage retrieval in the customs hall, bag drop at the United transfer belt, and full TSA screening at the Terminal 3 checkpoint. During midday arrival peaks when multiple widebody aircraft land simultaneously from Asia and Europe, queuing times at CBP and TSA can exceed 60 minutes.