This is posted at the suggestion of a museum colleague and describes a common enough event for frequent flyers but not, perhaps, for the casual traveler. A few years ago I was carrying two secured and hardened suitcases with important artifacts, bringing them from their home in a mid-western city to a museum where they would be on display for a few months. The owners generously agreed to the display but were cautious about their transportation. They required personal couriering and insisted that each suitcase get its own seat on the aircraft with special securing straps, duly paid for, of course; the cases were not to be placed in the hold.
The airline was happy to oblige and all was set. I was scheduled to take the next to last flight out when one of those famous mid-country storms blew up and the passengers in the waiting area began to queue up to be sure they got out that evening, trying to change their flight to the next to last flight rather than risk a layover should the last flight be cancelled. They had already become openly concerned about my carrying the two suitcases, and several business travelers mentioned I could not carry both cases on board; only one bag per passenger. Rather than explain my unusual circumstances, I merely thanked them for their concern. But as the weather looked bleaker and bleaker, these fellow travelers really hit the roof when they realized the cases and I were getting on that plane and some of them weren't. It brought out an unpleasant side of many folks which seemed unusual at the time (pre 9/11/2001), but seems pretty commonplace now--treasures or not. Just in case you wondered, the cases and I sat three across; I was offered but did not accept their share of flight snacks, and we all arrived safely.