Air Brake : George Westinghouse, U.S.A. 1911.

Air Conditioning : Willis Carrier, U.S.A. 1911.

Airplane : engine-powered, Wilbur & Orville Wright, U.S.A., 1903.

Airship : Henri Giffard, France, 1852; Ferdinand von Zeppelin, Germany, 1900.

Antibiotics : Louis Pasteur, Jules-Francois Joubert, France, 1887; discovery of penicillin) Alexander Fleming, Scotland, 1928.

Antiseptic : (surgery) Joseph Lister, England, 1867.

Aspirin : Dr. Felix Hoffman, Germany, 1899.

Atom : (nuclear model of) Ernest Rutherford, England, 1911.

Atomic Structure : Ernest Rutherford, England, 1911; Niels Bohr, Denmark, 1913.

Automated Teller Machine (ATM) : Don Wetzel, U.S.A., 1968.

Automobile : (first with internal combustion engine, 250 rpm) Karl Benz, Germany, 1885; (first with practical highspeed internal combustion engine, 900 rpm) Gottlieb Daimler, Germany, 1885; (first true automobile, not carriage with motor) Rene Panhard, Emile Lavassor, France, 1891; (carburetor, spray) Charles E. Duryea, U.S.A., 1892.

Autopilot : (for aircraft) Elmer A. Sperry, U.S.A., c.1910, first successful test, 1912, in a Curtiss flying boat.