Plane Change at London Heathrow
 

Will three hours be enough time to change planes at Heathrow? We will be arriving from Africa on our way to US so I assume we will have to clear customs at Heathrow. Will we also have to go back through security? Thanks.

Yes, it's enough time. No, you don't have to clear immigration or customs, provided your bags are tagged all the way through to the US. Yes, you will go through a security screening.

It will depend on your airline(s) and routes as to whether you need to change terminals. Follow the signs to "flight connections" when you arrive from Africa and you should have no trouble finding out where you need to go for the connecting flight. You will go through US immigration and customs at your first US landing point, regardless if you're doing a subsequent domestic connection from there.

Security there is a drag. But, based on our experience, if your flight is late to land, and you're in danger of missing your connecting flight, tell one of the staff members that's guarding the line, there's a good chance he/she will let you get to the front of the line. It happened to us.

ditto what Gardylook said. Also, check which terminal you'll be arriving into, and which terminal you'll be flying out of.

Then go to BAA Heathrow's website, and there's a tab for "flight connections". There are detailed directions for any terminal change combos; click on the one that describes your terminals and you can know ahead of time what to expect.

You will have to reclear security. The only reason you would have to collect your bags and go through customs would be if you are on separate tickets and the airline will not through-check your bags.

Otherwise, with through-checked bags, 3 hours is more than enough time.

We will be arriving on British Air and departing on American Airlines. We will not be checking baggage. Carry on only.

British Airways use T3, T4 AND T5. You need to figure out which terminal your flight arrives into.

AA uses T3 only.

If it's a T3-T3 transit, all you do is follow "flight connections to T3". You will have to reclear security even though you're staying in the same terminal.

If it's T4-T3 or T5-T3 transit, then you will first have a bus ride to get you to T3; then security.

I did a T5-T3 transfer last month, and it took only 40 minutes (from touchdown, to arriving at the T3 shopping area).

Wouldn't matter if you were checking, as BA will check through to AA.

Given your itinerary, 3 hours is plenty of time, maybe even too much time if things go well.