Normally when you fly to the US from other countries there's extensive checks of your visa by airline personnel. However Preclearance airports are somewhat special because there's CBP agents right there in the terminal and in theory the airline shouldn't care in the slightest if your visa is valid or not, as that's CBP's job to verify.

In practice, does this mean that airlines don't validate your visa when flying from Preclearance airports in Canada/Ireland/UAE? Or do they still send your APIS data to CBP and would refuse you entry into the Preclearance area if they receive a "Do Not Board" message?

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    Not relevant to US. But when crossing land border between Singapore and Malaysia, bus operators never ask for visa. As its very trivial to bring you back to the other side, if entry is refused. Commented Jul 29, 2022 at 2:04
  • @AnishSheela same for the US/Canada border buses.
    – JonathanReez
    Commented Jul 29, 2022 at 2:27

2 Answers 2


The airline will validate the passenger's ability to enter the US when the passenger checks-in at the publicly-accessible airline counter. Reasoning in reverse order from my memory of Preclearance in Dublin:

  • CBP doesn't issue boarding passes.

  • Thus, the passenger must have a boarding pass before being allowed to enter the US Preclearance area.

  • Thus, the airline must issue the boarding pass before the passenger is allowed to enter the US Preclearance area.

  • The airline must get APIS clearance before issuing a boarding pass, or refuse to issue a boarding pass if "Do Not Board" is returned.

  • Thus, the airline will submit APIS data in order to make the issuance decision.

  • I guess it's possible that you're able to tell the airline "lemme go talk to CBP" and they'll let you through? I've never tried it though.
    – JonathanReez
    Commented Jul 29, 2022 at 2:25
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    @JonathanReez Anything's possible...but I don't think they'd let you go through. Commented Jul 29, 2022 at 2:27
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    US CBP is located after security. Security will not let you through without a boarding pass.
    – Doc
    Commented Jul 29, 2022 at 2:38
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    @Doc there's ways to get past security (different checked-in ticket or connecting flight) but I assume CBP won't process you without a boarding pass to the US.
    – JonathanReez
    Commented Jul 29, 2022 at 4:35
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    @JonathanReez US Pre-clearance generally (always?) has a dedicated security area which requires a US boarding pass to enter.
    – Doc
    Commented Jul 29, 2022 at 16:05

You need a visa to get into the US. The airline and airport have to go through massive hassle if you turn out to not be allowed to board. Hassle enough it'll delay the flight and cost the airline a LOT of money.

And all because someone suspiciously didn't want to show his visa at the checkin desk. Which is unlikely to happen when a passenger has a visa...

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    In the question that triggered this question OP has a visa, in an old passport and a new passport without a visa, according to the embassy OP is allowed to enter the USA with this combination but the airline did stop them from getting on the flight. No 'did not want to show visa' but 'airline did not know the rules and stopped them'.
    – Willeke
    Commented Jul 29, 2022 at 13:29
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    The first paragraph of this answer probably isn't correct either. All the preclearance airports I know of that have moved the CBP behind security have done so by implementing a baggage handling system that holds onto the bags, only releasing them to be loaded on the plane after the passenger clears immigration and the officer has decided there's no need to inspect the luggage. There is hence little inconvenience to the airline if the CBP refuses entry, the bags (and passenger) just get sent somewhere other than the plane. This doesn't effect APIS, though, it works the same everywhere.
    – user38879
    Commented Jul 29, 2022 at 19:29

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