Clueless passport question

Stupid question. Is this right? ... We are traveling to the UK. San Francisco to London. My son is a dual citizen. He gives his US passport to the people in SF but when he lands he gives his UK passport. Right? But doesn't that confuse the airlines?  A "different" person arrives in the UK than the person left. Or am I over thinking this?

A totally confused mom. 

You are correct. Check in with US passport in the US, go through immigration in the UK with the UK passport. The airlines have nothing to do with it once he's checked in. The airline is only involved when he leaves, then immigration needs to see his passport when he enters the UK.

I am in a similar situation --- but I have got my US passport with my maiden name and my new UK passport with my married name - I was just going to travel on the UK one... is there a reason to use both??

Thanks!

Caroline

US citizens must enter/leave the US on their US passport (it's illegal for a US citizen to enter the US on a foreign passport), so you're fine to enter the UK on the UK passport but you should use your US passport to check in for your flight and you must use it for going back to the US. Travel must be booked in the name on the passport you are using though.