Does UK red-list rules apply to airside layovers (to US)?

I am planning a same-day layover at LHR (airside) from a red-list country to USA as destination (on h1b visa). Would that be allowed with current/upcoming rules? I have checked all rules at gov.uk but couldn't find anything explicit that layovers wouldn't be possible arriving from a red-list country.

Best Answer

According to https://www.britishairways.com/en-us/information/incident/coronavirus/entry-requirements the following applies to airside transits for destinations outside the Common Travel Area:

For destinations in the rest of the world (outside the Common Travel Area), you won’t need to stop your journey. You’re still able to connect flights at London Heathrow, Gatwick or any other UK airport, but you must stay airside (do not pass border control) and go straight through Flight Connections. If you do not pass border control, you will not need to quarantine. You still need to comply with the entry requirements for your final destination.

So yes, your itinerary is currently allowed, as far as UK Covid travel rules are concerned. The USA is a different matter.