Originally Posted by
lhrsfo
I never had a problem arriving in the US on my US passport and arriving in the UK on my UK passport. UA can keep both in its profile.
I once tried to. Enter the UK on my US passport and the Immigration officer was not happy: he made me produce my UK passport and told me always to enter on that.
This.
Always enter a country using that country's passport if you have it. You can leave the US on a US passport (no real checks anyways) and enter the UK on the UK one from the same flight. It is what you're supposed to do.