Originally Posted by
okrogius
If I had to guess you'd probably be asked during booking and check-in. Most likely you won't be able to get your BP until you provide this (I suppose they could refuse to fly you if you don't give this ahead of time, but this seems a tad unlikely).
Makes no sense though, since a huge part of the flying public books in shorter than 72 hour intervals. E-Fares would be practically useless. The weird thing is, I am sure UA already has my birthday and gender, which is all this really asks for.