When Microsoft put the original Flight Simulator program onto the market, in the early 1980s, I tried it for a while and then gave up. I had thought it would be fun to "take off" from Meigs Field, the airport on the Chicago lakefront where the simulator was programmed to start, and fly between the skyscrapers of the city toward whatever destination I chose. But the on-screen scenery turned out to be sketchy and uninteresting. Worse, I had no idea how to "land" the plane, at Meigs or anywhere else, and the program was not much help in teaching me. After ten or twenty flights that ended mainly with nosedives into the lake or countryside, I decided I could have more fun in other ways.

A dozen years later I became interested in learning to fly (and land) real airplanes, and I thought I should look at simulators again. There were now a range of programs, which were much more effective in teaching flying skills—or at least certain skills. They had also become a form of entertainment and virtual adventure captivating enough to attract vast numbers of users worldwide. According to Guinness World Records 2001, Microsoft's Flight Simulator had sold a total of 21 million copies by June of 1999.

Simulators' success is certainly deserved. Not many people fly real airplanes; fewer than 650,000 Americans are licensed pilots. But a larger group probably would like to fly. And even people who have almost no interest in flying (surely everybody finds it a little bit exciting to pretend to zoom through the air) or who view computer games as inherently creepy would find it hard to ignore the best modern versions. On a big, high-resolution computer screen you can find yourself facing an amazingly exact rendition of a Learjet cockpit, flying low over the Grand Canyon at dawn, with flashes of lightning visible in the distance, as you listen to air-traffic controllers direct you to the Flagstaff airport. You can take off in a pontoon plane from a lagoon in Bali, fly over paddies on the terraced hillsides, and then head toward Java's volcanic craters. You can approach Ayers Rock, in the center of Australia, and watch shadows move across it as the sun goes down. You can indulge in much of the visual romance of flying, without the time, expense, and training required to pilot a real plane.

These riveting effects are the result of an intriguing de facto division of labor. The programs themselves are all commercial products, from Microsoft and a number of small firms. But a wide variety of add-ons and improvements come from tens of thousands of hobbyists around the world, who spend countless hours polishing or improving some aspect of a program—and then post their work on the Internet for others to share. The flight-sim culture is a delightful reminder of a long-forgotten era, somewhere back in the 1990s, when people were excited about creating software for the new things it would let them do, not simply as a means of gaining market share and the grail of an IPO.

The flight-sim market resembles the rest of the software business mainly in that the most popular offering is from Microsoft. The current version of Microsoft's program is Flight Simulator 2000, or FS2000, which computer discounters offer for about $50. (A "professional" version costs about $70. It includes more simulated airplanes and a larger number of places whose scenery is presented in extra-realistic detail.) With FS2000 and most other programs you can "fly" from practically any point on earth to any other; the differences among the programs lie mostly in the degree of scenic detail, plus certain aspects of the airplanes' look and performance. With all these programs you can also specify the weather conditions through which you'll pass on any particular trip: clouds, wind, turbulence, rain. The fanciest programs let you download the real-time weather for your route, from aviation sites on the Internet. Then you can see what it would be like to pilot a plane from Buffalo to Detroit through the blustery night weather occurring just now. As with other Microsoft products, FS2000's strengths are related to its role as the industry standard. More hobbyists develop new airplanes or bits of scenery for this program than for the others. Its main shortcoming is its slow "frame rate," which can result in a jerky on-screen image if the program is run on what is now considered a slow computer or one without an up-to-date video-display card.

Although in many software categories Microsoft's product has become dominant, in flight sims there are still lively alternatives. The main ones are Flight Unlimited III (FU3), by Electronic Arts; Fly! 2K, by Gathering of Developers; Pro Pilot 99, abandoned by its previous owner, Sierra Software, but being revived by ETC Interactive; and X-Plane, developed and sold by one Austin Meyer, of Columbia, South Carolina. X-Plane sells for $39; the others cost around $20. Each of these programs has not only dedicated users but also a reserve army of hobbyists creating enhancements and add-ons. Devotees discuss the programs endlessly on the main flight-sim Web sites, which include avsim.com and flightsim.com, and the Internet newsgroup rec.aviation.simulator.

At these prices the other companies won't be able to pour money into further developing their simulators the way Microsoft can, and some of the competitors will probably disappear. But they have lasted this long—creating a far more diverse offering than is now available in, say, the word-processor market—for several reasons. Because they don't cost much, people can own several flight sims and enjoy switching back and forth. The switching is easy, because when the simulators are used with the right settings and equipment, they work in practically identical ways. The right equipment includes a joystick, which lets you steer the plane in a realistic fashion rather than by typing at the keyboard, and (okay, go ahead and laugh) a set of pedals that replicate the ones a pilot pushes to control the rudder of a plane. These attachments cost about $100 apiece; I use and like the Microsoft Force Feedback joystick, and Simped-variomodel pedals from the German manufacturer Hofmann. CH Products, of Vista, California, also makes popular pedals and joysticks. I don't want anyone ever to see me while I'm using this gear, but I do use it, because it makes the simulator feel more like an airplane—and reminds me that I'm not just sitting there doing my normal keyboard work.

A good reason to sample the full range of flight sims is that none of them does everything, but each excels in its own way. FU3 has great scenery for a few cities, and unlike FS2000, it comes with some built-in simulated air-traffic-control radio functions. You create a flight plan and the computerized controller tells you what to do ("Climb and maintain 10,000 feet"). But the program leaves out a lot of cities, and its renditions of cockpit instrument panels look primitive. Fly! 2K runs much more smoothly on-screen than FS2000 does, but it has blocky-looking scenery. Pro Pilot 99 also has a built-in air-traffic controller, and offers quick and easy ways to specify the conditions of your flight (where you'd like the cloud layers, what kind of turbulence you'll meet, and so forth). But the way it displays hillsides, mountain slopes, and other scenery is only so-so. X-Plane's enthusiasts say that its underlying mathematical design gives it the best "flight model" of all the simulators—that is, its computerized airplane responds to commands very much the way a real plane would. This is not by accident. Its thirty-one-year-old creator, Austin Meyer, has been an instrument-rated pilot since he was a teenager. He developed the program when he was in college, to help keep his instrument-flying skills from getting rusty. X-Plane is the one simulator that behaves anything like a real plane throughout the process of landing. Its scenery, though, is less impressive than the other sims'.

The good parts of all the programs keep getting better, because of those hobbyists and their burgeoning offerings on the major Web sites. Thousands of scenery supplements are available free for FS2000, and hundreds for the other programs. The big step toward dramatically more-realistic-looking scenery came when FS2000 was released, in the fall of 1999. Previous versions of the program had presented the world basically as a flat surface, onto which polygons representing mountains were plunked down. FS2000 introduced a far more accurate "terrain-mesh" system. Real-world data from satellites and geodetic surveys are mapped onto a topographic model of the earth's surface, with each square kilometer rendered at its actual average elevation. The "software developer kit" that Microsoft offers free with FS2000 allows hobbyists to apply the same approach and create much-finer detail using smaller geographic increments. I have admired scenery of, say, the area around Mount Fuji rendered with a mesh unit of fifty square meters—400 times as detailed as the basic one-kilometer mesh. Eddie Denney, a thirty-five-year-old staff sergeant and helicopter repairman in the Army, has used the developer kit to create a detailed topographic model of the United States that is available free at avsim.com and flightsim.com. Denney offers other scenery, for a modest price, at his own site, www.flightsimnetwork.com/realscene. He started by using a ten-meter-mesh unit to create models of the Grand Canyon and Mount St. Helens for his own amusement, and decided to post his terrain on the Web site because "everybody likes to share their work."

Other add-ons, most of which are free, let you fly different kinds of planes—the Spirit of St. Louis, Air Force One, the space shuttle. Hobbyists, largely in Europe, have created virtual airlines, with whole fleets of imaginary Airbuses and DC-10s that fly on schedule from London to Berlin and from Amsterdam to New York's JFK. I have visited a Web site run by a virtual air-traffic controller. Flight-sim users around the world send him their flight plans—say, Los Angeles to San Francisco, departing at noon. He tells them when they're cleared for takeoff and follows their route by way of Internet messages. A disproportionately large number of add-on planes are exquisitely detailed representations of Boeing 747s or 777s, with all the dials and controls in working order. With a good computer monitor, the right scenery add-ons, and the joystick and pedals, you can feel like an airline captain instead of one of the passengers habitually grousing in the back of the plane.

I asked several hobbyists, by phone and e-mail, why they had worked so hard to customize the aerial view of Boston Harbor or to re-create the cockpit of an F-18 only to give the results away. All of them said that they had designed the features because they wanted to use them on their own machines, and then saw no reason not to let others try them too. There's clearly a competition among hobbyists—a matter of pride rather than of money—to create the add-on scenery that gets downloaded most often (the sites keep count) or that gets the most-enthusiastic online reviews. The hobbyist-designers are an energetic subset of the general population of flight-sim users, attracted by the aesthetic appeal and the instructive aspects of pretending to fly.

The instructive aspects do not include teaching the basics of how to fly. Today's flight sims are at best neutral, and may even be harmful, in what is called primary flight training—learning how to handle and land a plane without killing yourself. Here the recency of my own primary flight training (I took flying lessons three years ago) may give me a particularly clear perspective, because I remember what it is like to learn. Although flying involves countless checklists and formal procedures, nothing really works until you have also developed certain instincts: how light a touch you have to use on the yoke, so you won't overcontrol the plane and send it porpoising through the sky; how the runway should look throughout the approach for landing if you want to be neither too low nor too high. The flight sims are poor at all of this. For instance, in a sim you can get a good look at the runway only when you're heading straight for it. In a real plane you're constantly looking out the side window to judge your height above the runway as you fly the prescribed rectangular pattern around the airport to prepare for landing.

But the simulators are extremely useful in the next stage of training—instrument flight. This is an intellectual rather than an instinctive process. The point of the training is precisely to teach you how to ignore the sensations of your body, which may misleadingly suggest that the plane is climbing or turning, and instead to keep the plane flying straight and level by continually scanning the instruments. You learn to navigate by interpreting fairly arcane needles and gauges—finding, for example, an imaginary intersection in the sky where the "255 radial" from one radio-navigation station crosses the "135 radial" from another. (A radial is a line drawn from a station at a certain magnetic heading: The 090 radial heads ninety degrees, or due east, from a station. The 180 radial heads due south. You work all this out on little dials.) For instrument training, flight sims are ideal. You change a setting to block the outside view with clouds, add turbulence or strong winds, and then use only the panel to see if you can get the plane to its destination. I spent many hours with Pro Pilot 99 and Jeppesen's FlitePro, a program designed solely for instrument training, before getting my instrument rating, two years ago, and I continue to practice, usually with X-Plane or FS2000, before taking real flights in the clouds.

If instrument training is the useful part of flight sims, the exhilarating part is taking off in a certain direction and seeing what wonders unfold beneath you. This, to me, is the engrossing part of real flying, too. You head east out of Seattle, and soon enough there's Idaho, and the open range of Montana, and the beginning of the Midwest. Everyone understands the concept of how the states fit together, but seeing them in one continuous band, from an altitude low enough to make out individual farmhouses clustered in the prairie, yet high enough to see the way rivers and ridgelines snake around communities, is very different from looking at a map. And to take off from Charles de Gaulle, circle the monuments of Paris, and then head north until the cliffs of Dover come into view is something I don't expect ever to do in a real airplane. The cliffs looked beautiful, just a moment ago, on my computer screen.

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