Posting from a 1st time Europe traveler with a tight itinerary - We are flying from Prague (depart 8:15 AM) to London-Heathrow (arriving 9:25 AM) on British Airways, and then from London-Heathrow to Dallas-FW (departing 3:15 PM) on American Airlines. No checked baggage, 1 carry-on each. Seems to me that this should be more than enough time to navigate between gates/terminals, clear customs, deal with departure delays, etc. etc.,...yes?
Should be a piece of cake. Arriving in London is generally efficient (depending on how many planes arrive at same time and where they are from). Even at its worst it has never taken me more than one and half hours to get through immigration (and customs)- and you possibly wont need to do that. You will probably end up with about 5 hours free within Heathrow, but they have pretty good shopping within the departure area. You should not have to go through customs and immigration, as long as you remain in the transfer /departure area. You will undoubtedly go through two or three security checks as you move from one terminal to another
Just pay attention to the terminals. British Airways uses both T5 and T3. If you need to transfer terminals, I highly recommend you use the airside connections bus, rather than exit and use the Heathrow Express to make the connection. The airside bus avoids going thru immigration, which can take a LONG time. We spent an hour in that line yesterday. To take the connection bus, just follow the purple signs that say "flight connections" and at some point you will have the choice point for the terminal you are going to. The whole transfer from T5 to T3 took us 30 minutes from the time we exited the plane to the time we were at the departures area in T3' waiting for our gate to be posted. If you have excess time, T5 is a lot nicer than T3.
Definitely follow Lola's advice and avoid immigration! That will save you a lot of time, but honestly you will have plenty of time! My flight from ORD ended up being late into LHR and I made my FCO flight in a different terminal with less than an hour to connect (mind you I skipped everyone in the security queue, but still) Having almost 6 hours will be quite easy!
Thank you for the tips...I really appreciate any advice on saving time and where to best spend extra time while waiting around Heathrow.
Nancy - Check out the Heathrow website - www.heathrowairport.com. There is a lot of information on making flight connections as well as what services are available at each terminal. We have made several connections through Heathrow over the several years. Most times we end up with 4 hours between flights and have never had a problem even when our inbound flight was really late. We have also never gone through Immigration unless we were leaving the airport. There are plenty of signs and people to help with connecting flights. Enjoy your trip!