21 January 1950 : Birth of Joseph Richard "Joe" Tanner, jet pilot, and NASA astronaut.
21 January 1945 : The British East Indies Fleet aircraft carriers HMS Ameer and HMS Shah support the landings of the 26th Indian Infantry Division on Ramree Island off the coast of Burma.
21 January 1945 : Task Force 38 aircraft fly 1,164 sorties in strikes on Formosa, the Pescadores, and the Sakishima Gunto, sinking five tankers and five other merchant ships and destroying two Japanese aircraft in the air and 104 on the ground. In Japanese air attacks on the task force, a bomber damages the aircraft carrier USS Langley (CVL-27) and kamikazes damage the carrier USS Ticonderoga (CV-14) and a destroyer; an accidental bomb explosion during a landing accident damages the carrier USS Hancock (CV-19).
21 January 1944 : Launch of Operation Steinbock (Baby Blitz), nocturnal WWII Luftwaffe offensive against southern England launched primarily for the sake of propaganda and as a measure of retaliation than for any military objective
21 January 1944 : Death of Heinrich Prinz zu Sayn-Wittgenstein, a German of aristocratic descent and a Luftwaffe WWII night fighter flying ace.
21 January 1944 : German ace Hauptmann Manfred Meurer is killed when his Heinkel He 219 night fighter collides with a British Lancaster bomber over Magdeburg, Germany. He has 65 kills at the time of his death.
21 January 1943 : Pan Am Flight 1104, a Martin M-130 nicknamed the Philippine Clipper, crashes into a mountain near Boonville, California, killing all 19 passengers and crew, including Rear-Admiral Robert H. English, commander of the U. S. Pacific Submarine Fleet.
21 January 1943 : The Combined Chiefs of Staff issue the Casablanca Directive. Its principal aim was to weld RAF and USAAF strategic bomber forces into one mighty air arm able to crush the German industrial, military and economic system.
21 January 1939 : Imperial Airways Short Empire flying boat Cavalier makes an emergency landing 285 mi southeast of New York due to loss of power and later sinks; 3 of 12 on board die.
21 January 1938 : First flight of the Potez-CAMS 141 ‘Antares’, a French four engined monoplane long range reconnaissance flying boat prototype.
21 January 1936 : First flight of the FMA AeC.3G, an Argentinian light utility aircraft, an evolution of the FMA AeC.3, first Argentine aircraft to be equipped with flaps.
21 January 1931 : First flight of the Vickers Type 161, a British unusual pusher biplane prototype interceptor, designed to attack aircraft from below with a single upward-angle large calibre gun.
21 January 1930 : First complete airport lighting system online at Calgary airport.
21 January 1921 : The first triple-triplane aircraft, and the first passenger-carrying aircraft designed to carry more than 100 people that actually got off the ground, is launched at Lake Maggiore, Italy. The flight attempt ends in failure when the 55,000 lb. flying boat nosedives into the lake.
21 January 1920 : The last Royal Navy balloon ship, HMS Canning, which has operated since December 1916 as a balloon depot ship, is sold.