Confused about new transit visa requirements for transiting through Heathrow

First, it is NOT a transit visa, it is an Electronic Travel Authorization.

Assuming you are both US citizens AND you are only connecting in London you do not need one. Read the official UK government site, ETA , for more information if you like.

Edited to add, click on the ETA link above. Under Contents, click on "When do you not need an ETA".
The 4th item down applies to you.

Just follow the signs at Heathrow for transiting passengers and you will be fine.

Are your flights on one ticket or two. If the former you will be fine without an ETA.

But, if you have booked two separate tickets for each flight and you are checking luggage you will have to go through UK immigration, collect your bags and re check them. You will therefore be crossing the UK border and will need an ETA. To complicate things even more, if you have two separate tickets, but only have carry on luggage and you can get your second boarding pass before you leave (so that you have it on arrival at LHR) you can still stay airside, follow the Flight Connections route and will not need an ETA.

That 4th point is not clear.

From the ETA Website.

you’re transiting through a UK airport and you will not pass through
border control - check with your airline if you are not sure

How do you know if you will not pass through border control? I wrote about this 3 weeks ago where I had a situation where I would be on one ticket but two different airlines and switching terminals. Not even the airlines could give me a definitive answer. British Airways, of all airlines told me to call my embassy.

Thanks all! We are on one ticket with British Airways both ways and will not need to claim and recheck bags, get different boarding passes or leave the terminal. Before writing this post, I did see that 4th point on the ETA website, but it wasn’t clear to me how they define border control . I’ve had layovers at Heathrow four times in the past couple of years and there’s always been some kind of passport check for transiting passengers as well as having to go through security before entering the terminal. Is this also considered border control?
By the way, British Airways also told me to call my embassy!

Go to this Heathrow Airport Connecting Flights site. Plug in your flight info and it will tell you what you will need to do.

For what you describe, you will not need an ETA.

Your pasport was checked by the airline because they have to make sure you have one. This is not Border Control. This is just an airline passport check.

Everyone transiting through Heathrow, unless arriving from a UK airport, must go through security. This is also not Border Control.

More than likely you won't have to change terminals. (The link in the above post will answer your questions.) Just follow flight connection signs.

I used flight connections a few days ago and it couldn't have been easier. The signage is very good. And I had to change terminals and airlines.

On a side note, even if you are changing terminals and airlines, you shouldn't have to go through passport control....unless....you have checked luggage that cannot be transferred automatically and/or you don't have the boarding pass for the second flight.

The airlines don't control "Flight Connections." Heathrow does.

While an ETA may not be required in your situation, I would still consider getting one. Here’s why. They are good for two years, take just a few minutes to apply for, and aren’t that expensive. If you have any irregular flight issues you have more options.

Why not just get an ETA? It doesn’t cost much. It shouldn’t take long? Is there some reason you think the request would be delayed or denied? When I’m on vacation I prefer to eliminate unnecessary worries. As much as I love this forum and trust its contributors, I would buy the cheap insurance and not count on this forum for my safety and convenience.