Help with LHR airport

Key information- is this all on one ticket or two separate tickets?

It's all 1 ticket -- booked through Delta but flights are operated by Virgin Atlantic (SEA - LHR) and Air France (LHR - CDG).

Heathrow has helpful information online about connecting flights through LHR.

https://www.heathrow.com/content/heathrow/main/gb/en/connecting-flights.html

https://www.heathrow.com/heathrow-blog/a-guide-to-connections

4 hours is plenty of time on one ticket. You can stay airside so won’t need to go through immigration and also will not need an ETA to enter the UK. Just follow the flight connections signs, which will lead to a bus to make the transfer between terminals. You will, however, need to pass through security again in T4.

Johnnew52: are you positive we wouldn't need the ETA to go through LHR? What I've seen seems to indicate it doesn't matter WHY you landed in the UK, only that you HAVE landed in the UK so you need it.

"What I've seen seems to indicate it doesn't matter WHY you landed in the UK, only that you HAVE landed in the UK so you need it"

Stick to official sources (see link below). You don't need an ETA if you're in transit. Just follow the Flight Connections signage.

"You do not need an ETA if ... you’re transiting through a UK airport and you will not pass through border control - check with your airline if you are not sure."

https://www.gov.uk/eta/when-not-need-eta

Incidentally, on your point 1, the UK was never part of the Schengen zone, so you always had to pass passport control and customs to enter. But you're in transit.

I just flew through LHR. I flew in from Amsterdam on KLM, arriving at Terminal 4, and flew out on Aeromexico from Terminal 3 on two different tickets.

I already had my boarding pass for the Aeromexico flight, and I was traveling with carry-on only. I did not have to go through passport control or customs. I assume if I had a checked bag, I'd have had to go through immigration and customs in order to recheck the bag. But if you have carry-on only, and you have your boarding pass, no one cares that you are flying on two different tickets. You can still treat it like a transfer and stay airside.

When I got off the first flight, I followed signs for transfer flights, and I arrived at a waiting area for the buses to other terminals. The bus ride seemed quite long, 15 minutes maybe. But with a four-hour layover, relax and don't feel like you'll need to rush.

Since you're all on one ticket, even if you have a checked bag, you won't have to go through passport control or customs.

Flight connections > bus > terminal 4 > security > but no ETA as you do not cross the UK border

I assume if I had a checked bag, I'd have had to go through immigration and customs in order to recheck the bag.

You would not have had to do so. Bags checked through Heathrow to another destination stay within the airline baggage system. Again, this assumes the flights are ticketed together.

Lots of extraneous information given.

When you check in for your flight you will get the boarding passes for both flights. If you have checked bags you wiill drop them in SEA and pick them up at CDG. (You will go through immigration and customs at CDG).

At Heathrow, just follow the purple signs to Flight connections. You will be led to the bus area where you will board a bus for Terminal 4. (Plenty of signage and people there to help if you need it.)

At Terminal 4 you will scan your boarding pass, go through security and then go to your gate. It's that simple.
.
You will not pass UK immigration or customs and you will not need an ETA.

You would not have had to do so. Bags checked through Heathrow to another destination stay within the airline baggage system. Again, this assumes the flights are ticketed together.

As I stated in my post, I was on two separate tickets. I realize that wasn't the case for OP; I was just offering additional information about connecting at LHR. An earlier responder asked if it was all one ticket; I was trying to explain that it doesn't matter unless you have a checked bag.

You are all wonderful! Thank you :) I'm feeling more comfortable with getting between terminals & the ETA.

Any thoughts on eating in the terminals or once we get to Paris (near the Catacombs)?

I literally just got off chat with the airline & the CSR said we WILL need the ETA even if we stay within the airport. You all sound very confident in your recommendation that we WON'T need it (and do a great job of explaining why FYI).

Is there someone in the UK(?) who can give a definitive answer for this?

Okay, I think I've answered it for myself (and anyone else who needs to know) on the UK website: https://www.gov.uk/check-uk-visa/y/usa/transit/somewhere_else. The info below is copied directly from there:

You'll need an electronic travel authorisation (ETA) to pass through UK border control

You do not need an ETA if you will not pass through UK border control. You should bring evidence of your onward journey, such as a ticket to your destination.

You always pass through border control if you:

• leave the main airport building for any reason
• need to collect your bags and check them in to your onward flight

You must also pass through border control if both:

• your onward flight leaves on a different calendar day to when you arrive
• there’s nowhere for you to stay overnight in the airport, for example in a transit hotel

The definitive answer was in the government advice in Simon's post above, one isn't needed as you should be remaining airside.
There is no reason why you would be going landside.

But I will caveat that. For what an ETA actually costs is it not worth getting one? If there is a heavy delay with the Virgin flight it is very unlikely, but not impossible you could miss the last AF flight of the night and have to go to a landside hotel.
Or there could (again exceedingly unlikely) be a strike in France or a security incident which has closed CDG.
As an example of extraordinary incidents a few nights ago at one of the minor London airports passengers were boarding a flight when a light aircraft crashed. The airport was immediately closed for the night, and passengers debarked and bussed elsewhere.
Very rare, but things happen.
Best to have a Plan B you never have to use-in this case an ETA.

isn31c, if it turns out one needs an ETA one can secure one online on-the-fly. I see little reason to spend the $$ ahead of time.

I usually agree with you, and your posts are immensely valuable, but IMO you got this one wrong.

I literally just got off chat with the airline & the CSR said we WILL need the ETA even if we stay within the airport.

I think the airline is hiring incompetents. I know, surprising, right? (Seriously, I believe they're giving a risk-avoidance answer in order to avoid lawsuits from US passengers, as we're notoriously litigious as a whole.)

You don't need an ETA, as you don't cross the UK border, even when travelling between terminals using Flight Connections.

However, with so much contradictory information, consider getting one as they cost so little, and then see if you cross the UK border while transiting at LHR and report back.

The scenario about having to go landside in the case of delays misses the point about the ETA. Your passport alone is enough to get you through the border. All an ETA is, is a pre-boarding check that the passenger pays for, and is done before travelling, thus reducing the number of checks that are done at the border.

Ranblin on is plain wrong. Without an ETA you are not crossing the border. If you have one (or not) It will show up on your passport when it is scanned at the border.
Some people on this forum have been denied ETA's. Applying 'on the fly' is an irresponsible suggestion, in case you are denied one - even if that is due to incorrect information on file.
Then is not the time to be appealing a rejection.

The process is quite simple in concept anyway for people who would have expected to transit, and who through no fault of their own doing now have an overnight stay.

If they already have in place the relevent documents to enter then they just present themselves to the border & they go off to the hotel arranged by the airline or themselves.

Those without such documentation are assessed individually by Border Force & either allowed temporary entry (& can then go on to hotel) or not. The latter have to stay in the overnight holding area in Terminal 3.

Okay, so it seems we probably won't need the ETA but safer to get it just in case. It's not expensive and is good for 2 years so I guess it gives us an excuse to travel that way again soon :) Thank you everyone for the help! ~ Lisa :)

Lisa, we got our ETAs for peace of mind prior to our recent trip as we were transiting through LHR. We got caught in an unexpected situation in 2023 (prior to ETAs) where our connection didn’t happen and we had to exit. I know there are strategies in place to deal with that situation but we also learned that after a LONG travel days our brains aren’t as sharp, so it seemed a small price to pay.