Time needed to change planes at Heathrow (separate tickets)

How do I say this? Do not do this
If you can do your check in online and print out your "boarding card" for the second flight to Zürich you will not have to go through check-in at Heathrow and stay "Airside" without going through immigration.

1) It will take 15-30 minutes after landing to taxi, de-plane and walk through corridors.
2) You will need to be at your departure gate 10-20 minutes before nominal departure time.
3) AND, transatlantic flights can be 1-2 hours late (or 1 hour early), depending on winds.

As you have done this as two separate bookings, Swiss are under no obligation to put you on a later flight if you miss your departure.
Short answer: How lucky do you feel?

You can just use connections without entering the UK. But the risk is all yours - be prepared to buy a new walk up ticket!

Have you already booked these tickets? We did that last year because we changed our minds after we'd booked the original tickets, but I wouldn't want to do it again.

Where are you seated in the plane? The closer you can be to an exit, the better your chances. We made it last year in late June in a little over an hour and that included going through immigration (customs doesn't really count because you just walk through), changing terminals and going through security again, but we were close to an exit.

FYI
United flights arrive in Terminal 2
and Swiss Air to Zurich departs from that same terminal 2

The customs officials at LHR can be very strict asking questions about your travel plans; so that you are not delayed please make sure you have your e-ticket in hand to show them.

I've gambled like this before and have never lost and it is easier when you are not traveling with someone;
you must have gotten a nice price to Zurich since you are risking this connection.

Transferring airside you will not talk to any "customs officials" or immigration officers either.

You can transfer airside even on separate tickets, IF you have carry-on bags only AND have your boarding pass for the onward flight. We have done this, transferring airside from T5 to T3. It was 45 minutes gate to gate. (We allowed 4 hours between flights so had lots of time to wait).

You are staying in T2, so should be OK if your incoming flight on United is on time. Since all kinds of things can delay a flight there is still a risk involved.

Go to the Heathrow Airport Flight Connections website and plug in your flights

You will see it does not say follow arrivals. It will say follow the "Flight Connections" signs. You will go through security but no need to go through immigration or customs. You will stay airside in Terminal 2.

Two hours should be enough time IF your arriving flight is on time. Very late and you are buying a new ticket to Zurich. And your return or any continuing flights on that ticket will be canceled.

Terminal 2 is the newest terminal with two floors of shops and restaurants.

Thanks, all, for the constructive input.

My Swiss flight to Zurich is not booked yet, but I was certainly hoping to minimize layover time. The next available flight is about another 1.5 hours later, aboard BA, departing from Terminal 5.

From the comments, I gather this additional time would be more than enough to manage the terminal change, with a total layover of 3.5 hours, but potential overkill if I could just stay in Terminal 2 with Swiss.

To be clear: Do I understand correctly that, if (1) I have my second boarding card and (2) I'm not collecting any baggage, upon arrival at LHR, I would merely go through arriving security, but not through customs or immigration?

(EDIT: Just saw Frank II's message, in which he confirms going through security but not immigration or customs. Thank you for clearing this up!)

Patty & Jazz+Travels mention passing through immigration & customs (respectively), but Lola indicates neither of these would be involved.

Therefore, if staying within the same terminal, my major risk items seem to be: (A) delayed inbound flight, (B) slow deplaning, (C) slow security, and (D) Murphy's Law?

Yes.

As long as you are not staying in the UK, you do not have to go through immigration and customs. Those who do either had bags to claim or didn't do their homework. (Sorry, that's how you learn for the next time.)

You don't say which airport your are departing from. Just realize that March can still get bad weather and delays. The terminals at Heathrow are huge and you could have to walk from one end to the other. Immigration lines can be long. I once flew into Heathrow when the rain was causing huge delays and we had to divert to Stansted for fuel.

By trying to go with the shortest connection time on a non-connected ticket, you are assuming all the responsibility of making it on time. And remember, it's not two hours. Boarding begins about a half hour before the flight and closes 10-15 minutes prior to departure. You miss it and all the flights on that ticket are trashed. That means if you have a return flight it will be canceled. You buy all new tickets at the highest price point. If you wanted to buy a ticket for tomorrow, the cheapest nonstop, one way, is $264.

Correct. Of those four possibilities, a delYed flight is the most likely. Our last four flights to Heathrow, in the past four years, have all been delayed by 30-60 minutes. All were on British AirwYs from Seattle. Only one of these was delayed in departure time (about an hour). Two were delayed in landing because of flight controls; we circled London 3-4 times which was a nice treat the time I was on the correct (right) side of the plane to enjoy the view. The fourth delay---50 minutes, was caused by a gate snafu---it would not connect to the plane, so they had to call for a truck to bring the stairs for deplaning. The first one was broken, so more delay. . . .

This was the one time we had to be somewhere---I had booked onward travel from London straight up to York. Fortunately I left plenty of time when I booked the train tickets, and we made it.

It just depends how risk-averse you are. Personally, I would rather spend an extra hour in the airport than stress over missing my flight. But is the later flight on BA leaves from T5, that adds another layer of complication. Dedicated buses for airside transfer between the terminals run every 10 minutes or less. But once you are at T5 you may have to travel to 5B or 5C after security. And the few times we have been through airside security at T5, it seemed rather chaotic--- and somewhat complicated by people with duty-free liquor, or water bottles they brought off the previous plane. But that was 10 years ago; maybe things have improved. Hopefully someone with more recent experience with that aspect can comment.

Hi Frank, thanks for following up. I'll be departing from San Francisco, which might not have its own weather delays in the afternoon, but I know it can be impacted by storms elsewhere.

Based on the collective input, the 1.5 hour-later BA flight is looking mighty competitive.

Thanks again to all!

If you do take the BA flight, make sure you have the right terminal as some BA flights leave from Terminal 3. Again, as stated, no need to go through immigration and customs. Go to the Flight Connections desk and they will put you on an airside bus to the proper terminal.

I'd suggest going to the website I gave earlier to get step by step instructions as well as look for how to access the satellite terminals in case your plane departs from one of them.

Thanks again, Lola & Frank.

I've decided to snub both the original Swiss flight and the BA flight, in favor of another Swiss flight with a longer 4-hour layover.

I expect I will appreciate the additional time on the ground so I can stretch my legs a bit after the long flight from SFO to LHR! And the extra couple hours are a small price to pay for risk mitigation. (Plus, this flight was cheaper than the other two!)

You might want to try this......let's say your plane lands on time and you could easily make the first Zurich flight on Swissair. You, as you stated, are flying that airline later in the day. Go to the gate of the earlier flight and see if the gate agents will switch you. You may get a lousy seat but if they are in a good mood, they might do it. They may not without more payment. You can then decide.

I've tried it a few times and sometimes it works. The worst they can do is say no.

I was afraid I was going to confuse you. I was just trying to show with all the extra steps, we still did it in an hour. We couldn't do "flight connection" because we had to check a bag. We flew BA from Seattle, added extra time during the flight because of a storm that forced us to fly farther north. Our 2nd flight was on Aer Lingus out of a different terminal. We had our 2nd boarding pass, but airlines are very sticky about transferring bags to a different airline. We had. 3 hour layover and that gave us plenty of time to stretch our legs and do a bit of shopping.

Patty, I don't know when you did your flight but in 2015 the parent company of British Airways took over Aer Lingus. Not sure if they will interline but I would be kind of surprised if they didn't. since most of their flights between the UK and Ireland are codeshares.

The same company also owns Iberia and Vueling.

British Airways doesn't interline checked bags on separate tickets - it will on a single ticket. This is a relatively recent change in policy.

I think it is quite likely that the OP will be hanging around the terminal for 3+ hours on the new itinerary ... but it is an insurance policy after all.

What Marco said.

We went last summer. We weren't sure if BA would issue the boarding pass for our second flight (coming from the west coast and having to add travel time to the airport put us out of the 24 hr check-in window), but we did get that. However, they would not check our bags through. Even codeshares won't do it anymore on separate bookings.

I'm just curious as to why you would book separate ticketed flight on United and Swiss Air. United and Swiss Air have some sort of partnership (Star Alliance). I booked my flight to Zurich through United but it is a code share operated by Swiss Air.

On a separate note, if you ticket through United, you can not get advanced seat assignments for a code share from Swiss Air.

i'd be a bit cautious. I flew last year from LAX to Edinburgh, with a switch at Heathrow. We had exactly 90 minutes.. We pretty much just made it through switching terminals, walking probably a good quarter mile, going through the motions etc (it was packed and they were doing construction on different parts of terminals). About 10 minutes to spare...

I'd probably give myself 2-3 hours if switching planes, airlines, needing to re-check in.

Heathrow has been permanently under construction since WWII. It may be finished by 2030.

Terminal 2 is rather less busy than Terminal 5, but has the drawback that there is only a walking route at present to the satellite, where transatlantic usually arrive.

Frank: If things go smoothly and we arrive with plenty of time, I will certainly try sweet-talking Swiss into letting me on the earlier flight. If not, no big deal!

Patty: Thanks for clarifying! Thankfully, it appears Swiss offers an "automated check-in" with electronic boarding card delivery, so I'm hoping that will keep things simple.

Edgar: The reason for the separate tickets is I'll be meeting family in England for several days after my journey to the continent, and we'll be flying back to SFO together. Booking the round-trip from SFO-LHR was significantly cheaper than the one-way, and my itinerary through Europe was not yet finalized before we booked the return flight to the US.

Hi - I am new to the forum and just found this thread by googling my question. My question is similar to this so i hope it's ok if I add on to this thread as I have a slight variation in my situation.

We (two adults and two teens) will be flying direct from SFO to LHR as the original poster was. We are not staying in London but rather traveling on to Amsterdam. The flights from SFO to LHR were hundreds less than flying direct to AMS so we figured we'd get a separate flight to AMS from London. We have booked the SFO to LHR part but not the flight to AMS yet. Our flight is supposed to arrive at 7:15 a.m. at LHR. The best price for a flight to AMS happens to be available on a KLM flight at 11:45. Our flight from SFO arrives in terminal 2 and the KLM flight is from terminal 4. This sounds like a lot of time even if our flight is delayed but what if we check bags under our original flight? How much extra time will that add on to the transfer process? Would we be in any danger of missing the 11:45 flight assuming normal delay possibility of up to an hour? Thanks very much in advance.

Leave double or triple the time they suggest or that you think is reasonable. Arrived at LHR on Friday. Left slightly late, arrived even later because of heavy air traffic at a peak time. Gate assignment delayed. LHR is busy and most transatlantic flights appeared to arrive late.

On our flight there was an announcement that there were some passengers with a tight connecting flight. They asked passengers not making a tight connection to stay seated until the other passengers left. Presumably we would know them from their stressed out expressions? I,be never heard this type of announcement before and thought it was a nice idea. After some sympathetic murmurings, predictably when the seatbelt sign was turned off, everyone around us stood and started collecting their things as normal. Oh, well

Also, Boeing 777W(?) is massive and takes forever to unload. Sometimes I consider the aircraft type. Easier to just allow a few more hours!

The checked bags didn't add significant time to our trip last summer. Because you are on two separate tickets, you have to go through immigration as though you were staying in the U.K.and then check back in again, as opposed to just connecting flights. Are your airlines partners? We could check in for our 2nd flight because our flights were on codeshare partners. But, we could not check our luggage through. The bags were waiting for us when we cleared immigration. Your timing is about what we had, but the previous poster is correct that your flight may experience trouble getting a gate, etc...It sounds like you have an agile group, so try to get to immigration as fast as possible. You will see some people practically running; they're trying to get to the front of the line.