We are using United FF miles to fly from LAX to VIE. First leg is United from LAX to LHR, where we have 1 hour and 40 minutes to clear customs/immigration and connect to our Austrian Air flight into VIE.

Will this be enough time?

Thanks.

We had an hour connection last month at Heathrow, PDX-LHR then LHR-CDG, both on British Air. I knew going in that it was tight but hoped for the best as both flights were in Terminal 5. Our flight from Portland landed on time and it was looking good until we hit the security line which was a mile long. My husband’s bag got pulled and it took at least 40 minutes for his “turn” to have it inspected. By the time he got his bag back our connecting flight had left. We had to wait 5 hours for the next flight; fortunately we were flying in business class so could use their lounge. Hopefully you’ll have better luck and you’ll make your connection!

There will be no customs or Immigration and your bags will be checked through to Vienna. (the UK is not part of Schengen so your are merely transiting - not 'entering' the UK). However you will have to clear security and a 1:40 connection at LHR can always be iffy - but neither Customs nor Immigration will be an issue.

I was posting the same time as tracilee -- their issues were security and T-5. Both Austrian Air and UA use T-2 -- which IME is the easiest/least screwed up terminal at LHR. But yes, 1:40 isn't generous.

Thank you both.