16 year old travelling LHR to Houston via BA – consent forms

When my son was 16 he flew with us on a separate booking to BOS. We had no issues on the way out, but on our return he couldn’t check in online, and when we went to the BA desk at the airport they said they needed to check that a responsible adult was with him. I’ve no idea how common such checks are but teenagers do travel alone all the time so it couldn’t have been a new situation for the staff!

So as @JDB says, some sort of written authorisation might be advisable.

For right or wrong. It being a daughter she will score higher on the trafficking checklist. Not knowing her personality it can’t do any harm for you to do a practice questioning session so she’s forearmed a little.
Who is she visiting – if not father then she should have some random facts about the person she’s meeting up with in her mind.
Who encouraged her to take this trip – Simple and straight forward but that person should be you, who’s also signed off on the form.
Why is she taking this trip – Whatever the actual reason is. If they pick her for extra questioning she is highly unlikely to realise it’s actually happening ( just as likely to be a check-in agent as it is anyone else) but the one thing anti-traffiking checks are designed to do are spot a conflict in the information provided and that is what is most likely to extend any screening.

US BORDER: As someone who travels to the US on a special visa so is subject to a secondary screen/ F2F meet up you should explain to her that if CBP have any concerns their end then she’ll be escorted by the officer she is talking to at the desk to a private area which could have many others sat in it. THEY GET REALLY PI**Y ABOUT TAKING OUT YOUR CELL PHONE IN THERE ( airport is irrelevant tbh, they don’t want you on your phone for numerous reasons you don’t need to burden her with knowing about) so tell her not to take it out of she is taken for secondary. She should though make sure she has a decent amount of battery on her phone and allowing for a long queue at immigration. If she is taken there then they may want to phone the person she is meeting, who should be at the terminal preferably. They may well want to check her phones messages/ WhatsApp/iMessage so you should let her know that that is pretty much SOP and it’s not coz they think she’s done anything naughty – it should be obvious to you the kind of things they’d be looking for.

Tbh if she’s a confident traveller then the likelihood drops off significantly but that might not be the case. More often than not they’ll check the paperwork and stamp her in. I’m not saying this to panic her or you but sometimes a little preparation can save a ton of angst or panicking. You know her best and if you think a pre departure chat about possible scenarios above might help or, as is possible, hinder her on her travels.