I'm trying to get clarification, and I cannot seem to find the answer that I need. We are leaving from Miami on October 18 to Nice, with a layover at Heathrow. As we are not leaving the airport, would we still be required to present results of a negative Covid test upon arrival at Heathrow? The AA website doesn't offer the information that I need, and the Us and UK travel websites are confusing me. Has anyone had recent experience with a layover at Heathrow just as a pass-through?

Not sure which UK Travel sites you are looking at but for UK info, the gov.uk website is the best ones to check. The answer to your question is on this page:

https://www.gov.uk/guidance/coronavi...hrough-england

Thank you.