Connection through Heathrow: Two Separate Tickets, Two Different Airlines/Terminals

https://www.heathrow.com/connecting-flights

A recent discussion on a similar question:
https://community.ricksteves.com/travel-forum/england/heathrow-transfer-process-2-separate-tickets

Start with this --- https://www.heathrow.com/connecting-flights -- to see what is involved with your flights.

What time of year is the trip? i.e., what are the chances for bad weather delays at JFK?

My travel will be in early May. Should be ok - weather wise.

Thanks for showing that link. My understanding is that I will land in Terminal 3, following the connecting flights signs, and have to go through security when I get to Terminal 4. Because I will only have a carry on, I won't need to go "groundside" and go through customs. No ETA needed?

Is that correct?

Have you already booked the JFK-LHR ticket? If not, and you specifically want to use AF and that specific flight to get to Nice, did you try "multi city" for your search with VA and find out their options?
As has been discussed here many times, with two separate airline bookings if your flight from JFK is delayed (or any other glitch) you'll have to deal with and pay for a rebooking when you arrive at LHR...
If you already have this ticket, it looks like great advice and strategies have been provided! I would add only to know alternative flights and carriers just in case, instead of starting that research upon arrival

To use Flight Connections, you also need to have the boarding pass for the Air France flight.

The Air France flight is a VS codeshare. But that is the only AF flight of the day whereas there are 6 BA flights to Nice a day.

From Heathrow connections-

You're not technically a connecting passenger if you've booked two separate flights. You'll need to pass immigration, collect your baggage then go through check-in, bag drop and security again.

[So if going through immigration you will need an ETA and will need to transfer landside]. Thus if you can't now change your ticket BA would be the better carrier. They leave from Terminal 5.

I think you will need an ETA. Your ticket from JFK only gets you to LHR. As far as Virgin is concerned, you are only travelling to the UK; therefore, they will expect you to have an ETA.

You're not technically a connecting passenger if you've booked two separate flights. You'll need to pass immigration, collect your baggage then go through check-in, bag drop and security again.

This assumes one has checked bags to collect and re-check.

The wording in the rest of the site seems to indicate/imply if one has a boarding pass ( or itinerary) they can use the 'connections' route and not pass through border control.
(As a connecting passenger, you can pass through security with just your itinerary in case you don’t have your boarding pass printed or at hand.)

No personal experience with this type of connection. My trips through LHR have been on single ticket BA connections

Given the ETA is only $15, it wouldn't be a bad thing to have it in case you do end up having to 'cross the border'. Having the ETA should make it go smoother/quicker, than not having it, to maximize your chances of making your 2nd flight.

if you have carry on only, what happens if the bag is gate checked?

if you have carry on only, what happens if the bag is gate checked?

It depends on the airline. I flew yesterday and a bunch of bags had to be gate checked . The could be picked up on the jet bridge as the passenger exited the aircaft.

Other airlines make you pick up the bag at baggage claim.

This does not sound like a very good deal. All you need is for the Virgin Atlantic Flight to be delayed to make the 2.5 hours 1 hour or less. Since you are looking at a separate ticket on AF, they are not going to wait on you if your VA flight is late and you can not make the connection. Delta has a nonstop from JFK to Nice, why not just take that flight. That is a code share with VA so you can book it through them.

Usually, when the OP has such flight itineraries is because they are getting a business class seat with points.

I came to read this thread for much the same reason as I look for train wreck videos on YouTube.