Do Airlines scan passport at check in before international flight when leaving theU.S. Or do they just look at it to make sure it is you?

Do Airlines scan passport at check in before international flight when leaving theU.S. Or do they just look at it to make sure it is you? - 1

They scan the numbers.

They scan the passport. The airline has an obligation to ensure that your passport is valid and that are legally able to travel to your destination. Otherwise, they can be obligated to return you at their cost if you are denied entry because of an invalid passport or other documents.

They scan it when you get to the airport. Then, as you board the plane, they check again just to make sure you didn't hand your boarding pass to somebody else.

The Airport / Airline has automatic Scanning machines.to check in and often to get through gates.
After that, once you have a Boarding Pass - the Pass has a bar code, and that does the work.

As you get to plane.
they often double check the passport AND the ticket are still matching (you have not been substituted for someone else)

Automated Passport Control (APC) - list of airports where it is operating
https://www.cbp.gov/travel/us-citizens/apc

example check in

TSA will of course check your ID before entering. The airline may ask to see it, but not scan it. Its mostly comes down to when you land abrod or return that they scan it then

AIRLINES are not and have never been IMMIGRATION or Passport Control for any country.

Do they look at your Passport? YES

Is your Passport Number sent ahead for destination place to check it out for hours before you get there? YES

Can various parts of Homeland security get information that you have a ticket? YES

Do assorted Police Agencies Monitor outbound Passenger lists for stuff? YES

Does the Airline Search out your Information associated with a Passport? NO
When you land that place with scrutinize YOU and your stuff. Their Immigration and Their Customs will do whatever it is they do. 200 different countries they DO NOT do identical things.
As they have a list of arriving passengers THEY KNOW YOU ARE COMING. They might have a special reception planned for you.

Your passport is scanned by security when you go through

Its scanned by the airline when you check in
Its examined by TSA when you go through security
Its compared (name) to your boarding pass as you board
Source
Frequent international traveler

Its checked by TSA and Customs.

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