A friend of mine

recently was going to throw away the return portion of a nonrefundable ticket, but since he ended up at the airport that day anyway (for a different flight on a different airline) he went ahead and checked in for this one (he's not saying which airline or where).
This made me wonder:
What can happen when you check in for a flight but don't get on the plane? He had a good excuse ready, and of course he didn't check bags, but what would the airline do if they realized it? He's worried more about what they'd do to his miles, but I'm wondering what they'd do operationally: hold up the flight? Search for contraband? Any ideas? Does it matter whether it's a small aircraft (easier to notice one too few passengers?) or large (more likely to use a computerized boarding gate?). And I suppose it would be really dumb to try this on an international flight.
In fact, he reports, perhaps the airline
knew he wasn't going to board the plane: he says it was the first time in several years that they failed to ask him the four silly security questions!
[This message has been edited by johna (edited 11-28-1999).]