For a guy who has been a model-airplane enthusiast since he was a kid, Hurst G. Bowers has the best job in the world. The retired Air Force colonel is museum curator at the Academy of Model Aeronautics in Reston, Va., where he oversees the museum's prized collection of about 400 of the finest model planes ever built. Crammed into glass cases and hanging from the ceiling of the building's circular atrium are replicas of the biggest names in aviation history - Santos du Mont's box-winged flying machine, World War I Fokkers and Nieuports, Charles Lindbergh's "Spirit of St. Louis," a sleek F-104 Starfighter jet, the space shuttle Enterprise.