About 16 years ago photographer John Schabel had the habit of taking his telephoto lens to the airport and shooting grainy black and white portraits of unsuspecting travelers as they sat on the runway. As Visual News points out, the photos were taken in the time of pre-9/11 airport regulations, and the most trouble he ever he ever found himself in was occasionally being asked to leave the airport. The passengers' faces are all mostly obscured to the point of anonymity, but their emotional states are very much intact. 

More portraits are available in his book, Passengers.