Later he pioneered the design of the cantilever-skin stressed wing that is now in general use.  He was a consultant to General Billy Mitchell in the historic airplane-versus-battleship tactical experiments of the 1920's, and as a special consulta nt to the U.S. Chiefs of Staff helped formulate basic concepts of air strategy in World War II.  He also contributed to the designs of the P-35 and P-43 which led to the development of the P-47 Thunderbolt, one of America's most effective wartime fighter planes.  Now a trim and sprightly man of 70, he still likes to take out experimental jet planes for a spin.

"The idea hit me as I was working on an electrostatic air-cleaning device which I had invented,"  the major recalled.  The gadget was designed to fight air pollution by electrically charging the particles industrial smoke and then trap ping them on a liquid electrode with the opposite charge."  De Seversky noticed an air flow developing between the two electrodes, caused by the ionization process previously explained.  "To an old flyer like me," said the major, "anything that stirs up a wind is a flying machine.  So I began to develop the idea."
The major seemed concerned that the Ionocraft might be mistaken for a kind of space vehicle.
"This is not a spacecraft," he explained emphatically to forestall any possible misunderstanding. "It's an airplane, designed to operate within the atmosphere.  But it will be able to do things that no present type of aircraft can accomplish."
Pointing out the potential advantage of Ionocraft over conventional planes or helicopters, de Seversky ticked off a whole string of radical notions:

High-altitude flight.  Helicopters whirl their blades in utter frustration at altitudes where the air gets thin.  Beyond 20,000 feet, they get almost no lift.  By contrast, experts calculate that the Ionocraft can kick up (or rather , kick down) enough air to stay aloft at 300,000 feet.

Unlimited Size. The bigger it gets, the better it flies.  Efficiency increases with grid area.  Disturbing airflow around the grid edge becomes proportionately less important in larger craft.  The reason:  Grid area increases f aster than circumference with growing size.  "We'll be able to build them as big as a city block," claimed de Seversky.

High Speed.  No practical speed limit has yet been determined.  The ions themselves flashing from emitter to grid impart to the air very high-velocity impulse.  Aerodynamic grid drag would be the chief speed limiting factor.  B ut streamlining of the grid edge and careful contouring of the craft, could minimize air drag.

Safety.  No moving parts in propulsion and no wear, mean less chance of failure, simpler maintenance.