Flying from Gatters to the US tomorrow. Have checked in and received the usual 'passport and visa check at the airport' message. Last time I went to the US in January I am sure I was able to submit my passport online via the BA app to have it verified and avoid the need to visit a desk. However this doesnt seem to be an option - wondering if this is a LGW vs LHR thing, or whether the functionality has been removed. I vaguely recall a thread about this being FLY related, so Heathrow only?

Without this will the Gatwick security scanners reject me, or can I just sail through and do the visa check thing at the gate?

Thanks