Originally Posted by SAT Lawyer

Anybody who you have the audacity to claim to be your companion, who is traveling on the same flight segment with you (whether on the same PNR or not), and who you are willing to escort on the airplane during boarding.

I suppose we can all conceive of a situation where somebody attempts to claim a random stranger as a companion, but let's face it: most of the time, we're talking about spouses, significant others, and children.

As for the specter of abusing companion privileges by making new friends at the airport, how frequently have you established such a strong budding friendship at an airport that you were interested in shepherding your new buddy through the bording process? Not very often, I'd suspect. And if you are gregarious enough and adventurous enough to make a new airport pal and willing to let him or her tag along with you at the gate, more power to you.