I'm also about to travel for the first time with both passports to the UK (via Toronto) and I think when my husband booked the ticket, he gave the airline my UK passport details. Does that complicate things? I'm assuming I can still fly out on my UK passport (as in, give that one at check-in because those are the details the airline has), arrive in the UK on that passport, and then present the UK passport at check-in when flying out of the UK but enter the US on the US one. Is that right?
Thanks so much!