Ed Swearingen's spectacularly fast SX300 was introduced to the aviation world in 1983, and the prototype's partially finished airframe was on display at that year's EAA convention. Swearingen chief test pilot Bob Thalman made the first flight of N300SX, a complex airplane with systems still being developed as construction progressed, on July 11, 1984, and it was at the EAA convention two weeks later.

Its debut at Oshkosh was quite successful, with a number of kits sold and a speed record set to underscore the design's principal reason for being-to go fast! Thalman turned a lap of 271 mph around the Oshkosh 500 racecourse to set a new NAA/FAI Class C.1b speed record.

The basic concept was to set new standards for Homebuilt or Amateur Built Aircraft as a dependable, fast mode of transportation; using all metal construction and proven techniques to provide an airframe that was equal to advanced jet aircraft. What a lot of people came to realize was that while the SX300 is an unbelievably wonderful airplane, it is also extremely complicated.

Although initially designed the airplane to accommodate a number of four- and six-cylinder Lycomings, Swearingen later standardized on the Lycoming IO-540 with a three-blade Hartzell constant-speed propeller. The factory prototype had a cowling with conventional air inlets, but subsequently a new unit with the now-familiar round inlets was developed.

The Swearingen does good jet-type high-speed aerobatics. Like the Marchetti, the SX300 flies a lot like a jet. The airplane is very capable of 280 knots indicated and a cruise of 240 knots at 18 gph. It's comfortable, the visibility is great and is a tremendous cross-country airplane.

Sanders Aeronautics maintain and fly this beautiful SX300 on a regular basis.