Note: Pro Pilot, released by Sierra in 1999 after it acquired subLOGIC, is an excellent update of ATP. Since Sierra has discontinued the game, though, you can check out instead Airline Simulator 2, a complete update of ATP based on an earlier remake by LAGO. This underdog adds three new aircraft (MD83, MD88, and B747-400) to the original classic, with new graphics, flight models, and scenery. Airline Simulator 2 is an immersive flying experience that includes 96 flights in Europe as a part of your "career" as well as more in the North Atlantic and the USA.
Note: in the "Extras" box below, you can download a zip that includes a number of scenery disks from subLOGIC and Mallard, thanks to Alan. These include SD-1, SD-2, SD-3, SD-4, SD-5, SD-6, SD-7, SD-9, SD-11, SD-12, SD-HAW, GB-1, GB-2, GB-3, MS-1 (Hawaii), MS-2 (Tahiti), and MS-4 (Japan). These scenario files can be used in Microsoft Flight Simulator 2.12, 3.0, and 4.0, as well as subLOGIC's JET, Flight Assignment: ATP, and Thunder Chopper.