The OP uses flawed reasoning. Supposed 120 people buy tickets and 110 checked in and 105 are at the gate. It does not purport to tell the airline that 110 are present but rather 10 people are not going to be on the flight which is critical in this day of overbooking and that 5 people are unaccounted for hence the announcements for people to come to Gate 17 or whatever.
Are you talking about before or after boarding? Before boarding is supposedly complete, the airline has no way of knowing that there are 105 people at the gate; all they know is that 110 people checked in.
After the boarding process is at least in principle complete, then they can see that only 105 people got on the plane (and they know who they are) and so can start calling names on the PA. I guess it’s a bit less work to only have five names to call rather than fifteen, but like the OP says, the check-in process seems a very cumbersome way to achieve that small reduction in workload for what amounts to a courtesy: “Passenger Smith, please see the agent at gate 47 immediately!” They don’t have to do that at all - "Sorry, sir, you weren’t here. We gave your seat to somebody else and the plane has departed.
Ultimately, a passenger is either on the plane or not; that is what ultimately counts when it comes time for the airline to start filling seats with standby passengers. Whether or not you have checked in, if you never show up they’ll fill your seat if they have people on standby.
As implied by others, boarding passes printed at home work fine. On SW, even when I check luggage (and therefore check in) I still use the printed boarding pass to clear security.
As for seat assignments, SW has no idea of who sits where, since you get a boarding number, not a seat assignment.
ETA: I’m sure someone with Photoshop skills could hack a SW boarding pass and get access to the gates without a real ticket, though probably you wouldn’t get on a plane. Since you still
clear security, it is not a big problem.
If this is true, then it would seem to be a compelling reason NOT to check in online (or any time before you get to the airport), as you’d be throwing away any insurance against something happening to prevent you making the flight.
Since I’ve never heard this before, and never heard advice to avoid checking in online, I’m skeptical that things work as you describe.
At PDX in the last year or two, they have started scanning the QR code on all tickets in the security line so they can see your name and flight info on the scanner as well as your boarding pass. You’d need more than just Photoshop skills to get past it.
I see. But you actually had a boarding pass (printed at home) as so you were checked in. You didn’t check in at the airport, buy you did on line
We know by testimony in this thread that they call people who have seats but who have not checked in before boarding. I’ve heard them call for people after boarding - I assume that these are people checked in and not yet boarded. They only get frantic if luggage is checked and not the person. I’ve heard them ask on the plane in that case, I guess to be sure that someone didn’t slip past without getting the barcode read.
Thanks everyone for the responses. Are there any people who work in the airline industry and can share a little knowledge about statistics? I guess for a question like that, it would be useful to know many seats are forfeited because the passenger didn’t check in, versus how many seats are forfeited because the passenger checked in but then doesn’t show up for boarding. If the second figure is significantly larger than the first (which I assume it is, since so many people check in online well ahead of the actual flight almost automatically, and airlines actually encourage this), then the added value of the check-in procedure doesn’t seem to me to justify the cost.
That’s exactly the point. There are many reasons why the database that counts is that of people who board the plane, not those who checked in for it. On top of the overbooking thing, another reason is immigration law enforcement: Many countries do not have immigration officials inspect people’s passports and visas when leaving the country on an international flight. Instead, they get the data of who was on the flight is forwarded by the airline to the immigration authority. The database of boarded passengers thus also serves to ensure that people do not overstay their visa.
I think that is an added bonus. I assume the main reason is suppose a plane holds 125 people. The airline will know ahead of time passengers <= 125 
or passengers may be > 125 potential :eek:
Interesting!
Yes, in that sense. Since you need some sort of boarding pass to get through security, and you only get one by checking in, you have to check in to pass security. But for all the airline knows you were hit by a truck after checking in and before making it to the airport. Since SW starts handing out numbers 24 hours before, there is a big bump at a day before the flight leaves.