Transfer from T5 to T3 at 6:15 in the morning

I believe you will be outside of security getting to T3 and if that’s the case, you may not have enough time even if your inbound flight IS on time which is a gamble to assume anyway. I recommend giving yourself a wider cushion. If your flight to the US is not on the same ticket as your flight from Dubai, that’s a huge gamble in which you might have to buy a brand new ticket to the US if you miss your flight at T3. That flight could close 30 minutes before departure. Keep that in mind as well.

It sounds like you’re on BA/AA? Provided the whole itinerary is on the same ticket, I wouldn’t really worry about it. The connection isn’t really that tight to begin with, and in the slight chance of a misconnect, the OneWorld JV has countless opportunities for rerouting.

Yes it is BA/AA and all on one ticket. Checked luggage through.

Not a problem.

When you arrive at T5, you do not need to go through UK immigration. Follow the "Flight Connection" signs and you will be shuttled over to T3 (you stay airside the entire time.) At T3, you will go through security and then on to your gate.

Fill in your flights on this website to get step by step instructions.

http://www.heathrow.com/flight-connections

Thanks, everyone. Haven't been back through Heathrow since 2019 so wasn't sure how things were now with all the chaos of travel these days.

The official 'minimum connection time' for this transfer route is 90 minutes so you almost have an hour in hand over this. Security time is the most likely potential uncertainty regarding the airport but people with upcoming flights are expedited to some extent.