Very few things can compare with the experience of flying 500 miles an hour "just off the deck," as military pilots say.
The world shoots by - "blurring to sheer verb," to borrow a phrase from poet Richard Wilbur - the aircraft aimed like a projectile hugging the ground, directed by imperceptible touches on the control stick, as if concentration and thought alone were making it happen.
In this high-tech age when so much of flying is computer-controlled, it's almost a throwback to seat-of-the-pants days when intuition and physical sense could be more important than rationality or logical judgment in determining an aviator's success - or survival.
Such flying is dangerous. When the earth is ripping by at a mile every few seconds, decisions must be made in far less time than that. Among the mistakes to be avoided are "keeping your head in the cockpit" - fixating on the multitude of instruments - or "letting your scan break down" (failing to constantly monitor what's happening both inside and outside the cockpit). Worst of all is "getting behind the aircraft," or letting things happen faster than you can respond.
There are two reasons to fly this low and fast. One is training for war. Attackers approach targets this way to avoid enemy radar that controls antiaircraft artillery or surface-to-air missiles. Some pilots train to deliver tactical nuclear weapons this way, popping up at the last minute to toss the bomb at the target.
It's not the kind of thing one can learn on the job in wartime. Perfecting such maneuvers takes constant practice, and it is not without mishap or close calls.
While practicing low-altitude "over-the-shoulder" bombing, I once pulled straight up into a cloud, began to get vertigo, and recovered only by flying straight back toward the ground, then pulling up in a gut-wrenching maneuver that rocketed me into Mexican airspace barely above the cactuses.
The other reason to fly low and fast is to show off, or "flat hat." There are many tragic stories of people doing this.
Hiking in the Sierras, I once met two old codgers who complained about "them jetters" who spoiled their solitude. I kept my mouth shut, knowing of friends who often checked the water level in favorite trout streams this way.
Today, legitimate training maneuvers still get mixed up with the impulse to stretch the allowable parameters just for fun - even to conduct a little impromptu air show to provide a cheap thrill for the earth-bound.
Skiing in Oregon's Siskiyou Mountains last year, my wife and I paused at the summit to take in the view. At that moment, two F-16s exploded past in a thunderous roar - below us and so close we could see the pilots' helmets.
* Brad Knickerbocker flew A-4 Skyhawk attack jets in the US Navy.