Once you’re on the plane, anything can happen. You can sit at the gate. You can sit on the tarmac. The pilot can actually park you on some remote section of the airport while you wait for whatever has caused your “on time departure time” to pass. I was on a 5 p.m. PHL to BOS flight once with images of petit filet and fine bordeaux at Grill 23 in my head. Instead, we waited and waited and my less than one hour jaunt took me 6 1/2 hours. Needless to say, I had some bland soup at the hotel. But, I also had learned this valuable lesson: Bring Your Own Water (and pretzels) because, while you do not know how long you will be sitting there, you do know that they will not feed or refresh you. On a flight from Denver recently my seat mate asked for some water during the boarding process. Nyet. He asked again a little later. Still Nyet. Then he begged. Finally, once he turned pale and said that he was going to pass out, they gave him some. Even if you’re in first class, go ahead and bring your own bottle. There is no consistency as to whether the flight attendants are actually going to serve you anything prior to the flight, so you might as well come prepared. Think of it as that $2.50 extra tax you have to pay at the airport, now that you can’t just bring your own from home. What other must haves must you have?