The scientific term for a fear of flying is "pteromechanophobia." It can also be called "aerophobia," "aviatophobia" or "aviophobia." By any name, it indicates the same thing: A fear of flying in an airplane, helicopter or other similar means.
Fear of flying is closely related to acrophobia, which is a fear of heights. Acrophobia is, in itself, one of the most common phobias among the adult populace of the western world. Fear of flying can also be related to claustrophobia, which is a fear of enclosed spaces. If you've ever been on an airplane, you know that even though you're out into the great wide open, the cabin itself can be uncomfortably cramped. Especially if you happen to be sitting next to Kevin Smith.
I, personally, had a mild fear of flying throughout most of my twenties, though it was never related to a fear of heights or a fear of enclosed spaces. Rather, it was a combination of a fear of death and a fear of not having control of the procedings.
By the way, isn't it weird that there's no scientific name for the fear of death? It's the one thing most of us fear the most, yet the scientific community has yet to name it. Maybe the theory is that it is such a prevalent and natural thing to fear that there's no sense in naming it. It's right to be afraid of death; it's not a medical or mental condition. It's simply how all living things are wired. You see it in nature as much as in human behavior; animals fight to their last to survive, no matter the situation.
Anyway, for me a fear of flying became closely related to a fear of death after the attacks on the World Trade Center's Twin Towers on 9/11. I was living in New York City in the time, and was able to watch the whole thing unfold from my front stoop. The end of my street used to end in a view of the twin towers, so I had a perfect view of the day's proceedings.
The fear of losing control is probably related to that day as well, since it's so well documented that the terrorists were able to take control of the airplanes before crashing them into the buildings, and no one on board was able to stop them. Anyone who's flown since then has to have asked themselves how they would respond in a similar circumstance.