Going through Heathrow to change planes - what's the process

If this is all on one ticket, you will stay airside for your transfer and there will be no customs or immigration. There will be a security check.

The Heathrow website has a connections guide. You can plug in your flights and it will give you instructions. The website is here:
https://www.heathrow.com/connecting-flights

Laura,

Thanks so much. The connections guide you linked to says we'll be in the same terminal for both arrival and departure and that we need 60 minutes for this -- so we have plenty of time!

That additional security check you will have at Heathrow is important and they are quite strict. You can help yourself get through quickly by preparing before you are at the security belt off loading your carryon. Liquids in ziplock bag and placed separately in the bin. If you refilled your water bottle for your last flight, make sure it is empty now. Electronics also must be removed and placed in the bins.

If you have to change terminals, there is a bus you can catch to take you there, both on the airside of the terminal. It does take some time but with 2h 45m you should be fine. Just follow the signs to the bus and it is easy to do that. Maybe you will be lucky and not have to do the bus transfer. If you do, enjoy the ride. It is pretty cool to see all the planes from ground floor level.

Confirming....this on one ticket and not booked separately?

If one ticket, even if you check luggage, it will be transferred to your next flight at Heathrow.

Yes, this is on one ticket. Maybe we'll just check the bags to go home, retaining medications and some other items in our carry-ons.

I'm trying to visualize how the security check occurs as we'll arrive and depart from the same terminal.

You are lucky that incoming and outgoing flights are in same terminal. One time our flights at LHR were so far apart that we had to taxi beteeen terminals!

Yes, this is on one ticket. Maybe we'll just check the bags to go home, retaining medications and some other items in our carry-ons.

Never put medications, valuables ,electronics, or anything you really can't afford to lose in checked bags.

I'm trying to visualize how the security check occurs as we'll arrive and depart from the same terminal.

You will be routed to the security area. You will have no choice. There is a different entrance than coming from the main departure are.

One time our flights at LHR were so far apart that we had to taxi beteeen terminals!

You should never have to do this unless you are on two separate tickets and have to retrieve luggage.

I echo the comments above about how Heathrow security is strict about liquids in one quart sized Ziploc bag, based on personal experience when I connected there after my France tour last year. Before you even get to security, be prepared so you can make everything easy and smooth for yourself.

I still don't understand how one goes through security when the arriving and departing flight are in the same terminal. If you have seen or experienced this, please describe this. Thanks!

I still don't understand how one goes through security when the arriving and departing flight are in the same terminal. If you have seen or experienced this, please describe this. Thanks!

You will follow the signs for ”flight connections” after getting off your flight which will route you through a security area for connecting passengers. It is all well marked.

As Laura stated, you are not going through the main security area. It is a specific security area for connecting flights. You have no choice. You will be routed to this.

I'm guessing you're thinking this is like when you arrive at the airport and go through security. That's not this. It's a separate area. Thousands of people do this every day without problems. Don't worry about it.

ASF, while I haven’t gone through Heathrow in a while, I have raveled through other European airports on the way home to the USA. Many times I have flown from a European city to another European city for the transatlantic flight to the USA. Yes, I passed through security at the originating airport, only to have to do so again in the major airport where I am connecting to the USA bound flight. And yes, sometimes in the same terminal, tho perhaps having to go into an area or wing where all USA bounds flight board. The second security, I think, results from the requirement of the USA Homeland Security people. I suspect our USA requirements are sometimes stricter than the European requirements. And all flights headed to the USA must meet USA requirements.

Actuality I have had the same experience of going through security in a major airport, and then doing it a 2nd time in the same airport for USA bound flight. Everybody would go through the initial security just past the ticketing area, and then USA bound people would have to go through the second station, as described above, to the area where all USA bound flights board and depart.

We made a plane change in Heathrow a couple of weeks ago. Brit Air Rome to Heathrow, terminal 5, and then on to Seattle. Baggage checked through.

The security check system is well described above. Not a problem. Once through security you are in the very large and somewhat confusing Terminal 5. Like many European airports departure gates are often not posted until as late as 30 minutes before boarding. Because of the size and somewhat confusing signage it can take 20 minutes to find your gate. Just be alert.

You say both flights use the same terminal. I assume this is T5? T5 actually has 3 separate buildings, connected by an underground train. You could well land at a 5B gate and depart from 5C, but you cannot go straight there.

Passengers arriving at Heathrow, regardless of the terminal, have only choices: follow the signs to Passport ControlArrivals to go through immigration and leave the airport, or follow the purple “Flight Connections” signs to stay airline and reach your next flight—-after passing through the security check. There is no possibility of circulating freely around the airport to get to your next gate. It may not even have been posted yet.

Watch these purple flight connection signs carefully when you deplane, because at some point they will divide between passengers staying in T5, and passengers going to other terminals. Don’t just “follow the crowd”, keep checking until you are on the correct path.

The path to remain in T5 will take you to the underground train to 5A (unless you land at 5A). You will exit the train and reach the security area dedicated to connecting passengers. As noted above, they are strict—make sure you have emptied water bottle and removed tablets and laptops from your bag.

Once through security, you are in the main transit area of T5A. Plenty of shopping opportunities and some for a meal or a snack. But your first task is to find a Departures light board and see if your next gate has been posted yet. If not, keep checking every 10 minutes or so. Once it is posted, head to the gate, especially if it is a higher-numbered gate in 5C. You will take the train to either B or C. If the flight leaves from an A gate you just make your way there. But I will note that every US-bound flight we have taken on British Airways, whether to Seattle or San Francisco, has departed from 5C. But maybe other US cities get different gates.

Regardless of where you are going, you must pass through UK airport security unless you have done so at another UK airport. It has nothing to do with USA flights.

This has been so enormously helpful. Thank you!! Now I won't spend time before and during my trip pondering the possibilities of what happens at Heathrow. I'll know because you all are so great.