Originally Posted by
meFIRST
The second check is unique to United, specially I have found, to stations that used to be Continental, because its an old continental practice. ( In my observation pmUA did not do this)
Are you referring to flights to Canada specifically, or international flights in general?
As previously mentioned, Canadian regulations require a doc check on boarding or at the gate for all flights to Canada. Doesn't matter who you're flying - it must be done. IME, sometimes, the GAs will announce passengers can come to the podium, shortly before starting boarding, mark it off, and then just the BP at actual boarding. Some just check when you board. Depends on the GA. Some like doing it some way, some the other. I travel between US and Canada several times a year, almost always on UA, and this is always how its been done, at least for the last ~10 years. On AC, its usually only done while boarding. Any airline who isn't checking passports on boarding to/from Canada is breaking the law, and is liable to be fined for it.
International is likely different. May not be legally required to be done, but some carriers do anyway. UA usually does. Visa/passport check. As mentioned before, they don't want to be fined for transporting someone without proper documents to enter the country they are traveling to. Its not a cost-cutting thing (as someone mentioned upthread) - its wanting to double-check so they are not incurring costs/hassle they don't need.
Internationally, it can be done differently on different carriers and from/to different destinations. I say that having just returned from a year living in BOM and having flown several carriers internationally. TK, TG and CX, for example, don't check passports at the gate for their flights to their hubs. But do check passports/visas returning back to BOM (not sure if that's a requirement, or just covering themselves). SQ does check on their flights to Singapore from BOM, IME. And despite the fact that TG doesn't check passports ex-India - BKK, they insisted on seeing a passport before I could board my domestic BKK-KBV (and return) flights.
Another story, I was coming back to Canada, BOM-ZRH-YYZ. Boarded LX in BOM and everything was fine. At ZRH, boarding to YYZ, AC had some outsourced security folks checking passports just in front of the gate, then when boarding, the GA was checking passports also. I got called aside because the birthdate they had in the APIS for some reason didn't match the one on my passport. So I had to wait while they checked it out and switched it.
It is what it is and not that big a deal.