- Terminal 2 — Home to Star Alliance airlines like Singapore Airlines, Lufthansa, United and Air Canada
- Terminal 3 — Home to most Oneworld airlines like Qantas, American Airlines, Cathay Pacific and Japan Airlines, as well as some British Airways flights, and Virgin Atlantic, Delta and Emirates
- Terminal 4 — Home to SkyTeam airlines like Alitalia, KLM and China Southern, as well as most Middle Eastern airlines (excluding Emirates) like Qatar, Etihad, Gulf Air and others
- Terminal 5 — Home to most British Airways flights and Iberia
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If you have a connection in the same terminal, such as from one Star Alliance flight to another, this should be a fairly straightforward process to transfer 'airside' without entering the country or passing through immigration. You simply follow signs to transfers, pass through transit security in the same terminal and walk back into the departure lounge area for your next flight.
This experience will be similar to transfers you might have done at other airports.
But if you have to transfer from one terminal to another, the process is more complicated. Fortunately, the way most airlines are grouped together minimises the amount of passengers requiring transfers from one terminal to another. However, the split of British Airways between Terminals 3 and 5 can see many passengers transferring between the two.
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Although some of the terminals are a fair distance apart, Heathrow runs airside transfer buses between terminals for those passengers who have to transfer from one terminal to another. These buses depart every six to 10 minutes.
British Airways states that you should expect a transfer time of around 20 minutes using the Flight Connections bus, excluding wait time for transit security at your new terminal if transferring between Terminals 3 and 5 (in either direction).
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Heathrow published the following short video explaining the process.
Here are some general tips on transferring terminals at Heathrow:
- You will need to have an onward boarding pass in order to transfer to another terminal (or pass transfer security within the same terminal). If, for any reason, you were not provided with a second boarding pass when checking-in for for your first flight (i.e. the one to Heathrow), you can obtain the onward boarding pass at the connections desk in the terminal at which you land.
- It's best to transfer to your second terminal as soon as possible after landing, even if you have a long connection. There will be far more facilities in the departures area of the terminal than the transfer area.
- If you have lounge access, you won't be able to access the lounges in the Heathrow terminal at which you land if different from your departure terminal, no matter how good they are. You will need to transfer to your next terminal and access the lounge there with your onward boarding pass.
- If your connection is on a single ticket, any checked luggage will be transferred automatically from one flight to the next and you will not have to collect it. If your flights were booked separately, ask at check-in if the first airline has an interline agreement with the second airline. If they do, they should be able to check your luggage through to your destination. If not, you may have to collect your luggage yourself by entering the UK at the immigration border, moving to the new terminal with your luggage land-side rather than airside (which is a different process), checking your luggage in with your new airline and passing through normal security there.
- If your connection is on two separate tickets, it is usually easier to travel with hand luggage only, if possible.
If you're still unsure of the process, Heathrow Airport has a journey planner where you can enter both your incoming and outgoing flight number and it will give you a step-by-step process.
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