by Joseph F. Alcock 

Tony LeVier, an American pilot; Frank Whittle, a British inventor, and Kelly Johnson, an American Aircraft designer; developed the first operational jet aircraft in the closing years of World War II. Their stories and a brief history of some of the significant aircraft that followed their first jet are included in Tomorrow is Supersonic: The Story of the Jet Age. 

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Excerpt from the Prologue to Tomorrow Is Supersonic: The Story of the Jet Age:  

As I approached the sound barrier, it seemed a thousand hands were pulling back on the airplane, as if it were reaching a wall that was impenetrable.  Then suddenly something released, and the airplane shot ahead.  It is true, there is a wall there — a wall of tremendous drag — once you have reached the speed of sound and the compressibility effects are stabilized, drag suddenly changes, and the airplane slips on ahead as though it were on a greased platter.  The sound level even changes.  The air rushing over the airplane and the roar of the engines behind you all add up to make noise, but as the speed of sound is exceeded this noise can no longer reach you, and you are ahead of this noise, traveling faster than sound, that is supersonic.  The sudden change in the sound level was one way I knew I had gone through the barrier. 

As I passed it my Mach indicator stood at 1, and I said over the radio, “There she is.” My speed was near eight hundred miles per hour and altitude about twenty-seven thousand feet. 

— Tony LeVier describing his first supersonic flight in the Lockheed F-90 swept-wing fighter over the Mojave Desert in southern California in April 1950.