I work in a bar as both a server and a bartender. It is our corporate policy to card everyone regardless of age or appearance to not only cover the company from underage drinking liability, but also to prevent discrimination charges in the event of an absurd lawsuit over something that happens in the bar. It's unfortunate in some instances, because I agree with others that many older customers are NOT flattered at being carded, they get angry.

If I card someone and they do not have identification, I am legally not allowed to serve them alcohol. It doesn't matter if they are 50, 100, or 150. If it's my own grandfather. If the server is aware that the person does not have I.D., it is against the law to serve. I'm not sure if that's a state law or federal, but I've received training in VA, PA, and TN, and that was always the case. My boss tells me that it has something to do with the "Patriot Act" (don't quote me on that) or something that requires people to carry an I.D. at all times, but there is in fact no such federal law. However, even though there's no law.. if an ABC (alcohol and beverage control) agent comes into the bar and asks a patron for ID, and they cannot produce an ID, it can be up to $5K in fines for the bar, $10K in personal fines, loss of beer/liquor license for the bar (which is thousands lost in revenue), and jail time. While that's unlikely to happen, other things do happen while alcohol is involved, such as bar brawls. While I don't see that happening in an airport bar, I guess it's possible. And the police would probably have an easier time identifying someone if they have an ID.

The only other reason that I can think of to card people in an airport bar is as a security measure. If you ask someone for an I.D. and they can't produce a driver's license or passport, that is a giant red flag that something might be wrong, as there is no way they should have been able to get past airport security to enter the gate area.