Heathrow and Frankfurt Conncections

Heathrow and Frankfurt are good airports but LARGE airports. I have made 1 hour connections in both but not by intent. When I travel I generally do end up in one or the other and I try not to get a flight with less than 2 hours especially on United because I seem to have miserable luck with their flights being on time.

You always need to go through security when changing planes at Heathrow. Changing all within T2, there's a LOT of walking, but the terminal is newly renovated, the signage is excellent, and anywhere there are stairs, there's also a clearly labeled lift. Sixty minutes sounds right to me, as long as you land on time and keep moving (no stops for bathroom, shopping, etc).

You should not need to go through passport control in London if you are going from the US through London to a Schengen destination (or the reverse).

If you are going from Barcelona or Paris through Frankfurt to the US, you WILL need to go through passport control in Frankfurt, as that's your exit from the Schengen zone. You also need to go through a second security check right at the gate (usually doesn't take too long, but of course no guarantees).

I agree that while you may make a one hour connection in either airport, you will have lower blood pressure if you allow more time. As said above, both airports are huge and always busy, and if there's any disruption for any reason, you could be slowed down - and miss your flight.

So our flights are booked! I think we'll be OK as long move along. Thanks for the advice.

SFO to Heathrow to Frankfurt - 1 hour 20 minute layover in London
Heathrow to Frankfurt to Barcelona- 1 hour 50 minute layover in Frankfurt

I connected through Heathrow on United to Swissair, the terminal is very large, you will likely walk ALL the way from one end to the other on one level, rise up and walk back again to your new gate, you will go through security even though you haven't left the airport, there is a table full of baggies and you should just zip up everything loose of note in your carryon even if they said it was OK at your departing airport. Better to overbag so you don't have to go back and bag some more. They're British, so they speak the language and are pretty friendly for civil servants.

The UK in effect trusts no other airport security other than that carried out under its own supervision. In that regard they are the same as the TSA.

I wouldn't mind the belts- and-suspenders approach to security if I had at some time passed through an unsecured part of Heathrow, but the way it's set up when connecting that is not possible so it's just an aggravation. Oh well.