N421EF

N421EF is a Textron Aviation AS 21, a twin-engine jet operated by SOARING SOCIETY OF BOULDER. SkyMeter has tracked 1,078 flights totalling 800 hours of airtime via ADS-B. The most frequent segment is KBDU to KBDU. Service window in our records spans 441 days. Of those flights, 100 (9.3%) carry at least one detected incident: a go-around, unstable approach, stall warning, or runway excursion. The Textron Aviation AS 21 has a maximum takeoff weight of 6,000 lb, light wake category.

About the Textron Aviation AS 21

The Aero L-29 Delfín is a Cold War-era jet trainer that became the most widely produced jet training aircraft in history, with over 3,600 built between 1963 and 1974. Designed by Czechoslovakia's Aero Vodochody, the L-29 was selected as the standard jet trainer for the entire Warsaw Pact, serving air forces from East Germany to Egypt. Its rugged construction, docile handling, and simple maintenance made it ideal for ab-initio jet training, introducing thousands of pilots to jet operations during the height of the Cold War.

The straight-wing design and side-by-side seating were unconventional for a jet trainer but contributed to its forgiving flight characteristics and excellent instructor-student communication. Powered by a single Motorlet M-701 turbojet producing 1,960 pounds of thrust, the Delfín cruises at around 340 knots and can reach altitudes above 36,000 feet, though typical training missions operated much lower. After the fall of the Iron Curtain, hundreds of surplus L-29s entered the civilian market, where they found new life as affordable warbird aircraft for aerobatic displays, formation flying, and jet transition training.

Today the type remains popular in North America with warbird collectors and flight schools offering jet upset training, prized for its relatively low operating costs compared to Western jet trainers and its honest, predictable handling that forgives student errors while still delivering an authentic jet experience. SkyMeter has tracked flights across airframes and operators, with the largest observed operator.