The United States replaces the national insignia for its military aircraft adopted in September 1943 with a new marking consisting of a white star centered in a blue circle flanked by white rectangles bisected by a horizontal red stripe, with the entire insignia outlined in blue , which is still in use in the 21st century.
February 25 – The U.S. Joint Chiefs of Staff recommend that the United States use atomic bombs early in any war with the Soviet Union and call for an increase in the American inventory of atomic weapons.
March 3 – In Naval Strategic Planning Study 3, the Strategic Plans Division of the Office of the Chief of Naval Operations asserts that U.S. Navy aircraft carriers will be able to operate successfully against the coast of the Soviet Union in the face of substantial land-based Soviet air power, stating that the carriers are "the only weapon in the possession of the U.S. which can deliver early and effective attacks against Russian air power and selective shore objectives in the initial stages of a Russo-American conflict." The findings anger U.S. Air Force planners, who view strategic attacks against the Soviet Union as a strictly Air Force mission.
May 1 – United Airlines begins daily scheduled service between San Francisco and Honolulu.
May 15 – The U.S. Joint War Planning Committee reports that the Soviet Air Force has 13,100 combat aircraft and that the Soviet satellite states have another 3,309, and that a month after the beginning of mobilization this could increase to 20,000 Soviet and 3,359 satellite state aircraft. It estimates that in an offensive in central Europe, the Soviet Union would employ 7,000 attack aircraft
May 29 – The Douglas DC-4Mainliner Lake Tahoe, operating as United Airlines Flight 521, fails to become airborne while attempting to take off from LaGuardia Airport in New York City, runs off the end of the runway, and slams into an embankment, killing 42 of the 48 people on board. It is the worst aviation disaster in American history at the time, although the death toll will be exceeded in a crash the following day.
May 30 – During a flight from Newark, New Jersey, to Florida, an Eastern Air Lines DC-4 disintegrates in flight at an altitude of 6,000 feet (1,829 m) and crashes into a swamp near Baltimore, Maryland, killing all 53 people on board. It replaces the previous day's United Airlines crash as the deadliest airline accident in American history. Among the dead are two relatives of a man who had died the previous day in the United crash. The 97 deaths in the two crashes exceed the entire commercial aviation death toll in the United States for 1946.
June 24 – Kenneth Arnold is piloting a CallAir A-2 at about 9,200 feet (2,804 m) near Mineral, Washington, when he sights what he reports to be a group of disc-like unidentified flying objects flying in a chain which he clocks at a minimum of 1,200 mph (1,932 km/hr). He refers to them as looking like saucers, leading the press to coin the term "flying saucer," which soon enters everyday speech.
June 30 – The Evaluation Board for Operation Crossroads submits its final report on the July 1946 atomic bomb tests at Bikini Atoll. It finds that an atomic attack could go beyond stopping a country's military effort and in addition wreck its economic and social structure for lengthy periods, and could even depopulate large portions of the earth's surface, threaten the existence of civilization, and cause the extinction of mankind. It recommends that the United States develop a large inventory of atomic weapons and the means to deliver them promptly and be prepared to strike first, with legal authority to launch a massive atomic strike to preempt a foreign strike if there are indications that an adversary is preparing one.
July 15 – Northwest Airlines launches the first commercial passenger service from the U.S.A. to Asia's Far East along the North Pacific route with Douglas DC-4 The Manila, linking Minneapolis/St. Paul (USA) and Tokyo (Japan), Shanghai (China) and Manila (Philippines) by way of Edmonton (Canada) (technical stop), Anchorage (Alaska USA) and Shemya (USA) (technical stop). The Northwest Seattle—Anchorage service offered a connection (at Anchorage) with this new operation to the Orient. Seoul (South Korea) was included as a stop on the Northwest Airlines route to the Orient in August 1947.
Bad weather forces a U.S. Marine Corps pilot down in communist-controlled territory near Tsingtao, China, during the Chinese Civil War. A landing party of U.S. Marines and U.S. Navy sailors destroys his plane to prevent its capture but fails to retrieve him, and the Chinese Communists return him to U.S. custody only after lengthy negotiations.
August 4 – In an assessment of the defense of the Iberian Peninsula from Soviet invasion if Soviet forces reached the Pyrenees, the U.S. Joint Warfare Planning Committee reports that the Spanish Air Force has only 330 combat aircraft, all obsolete, and that the Portuguese Air Force is small and also obsolete, and that they would face about 1,000 Soviet aircraft. It finds that a defense of the peninsula at the Pyrenees would require the deployment of 739 ground-based combat aircraft and nine aircraft carriers to the area.
September 23 – The U.S. Joint Chiefs of Staff recommend that the United States Government pass legislation authorizing the United States Armed Forces to launch an atomic attack on the Soviet Union if one is required to prevent a Soviet atomic attack on the United States.
September 30 – The U.S. Joint Warfare Planning Committee reports that the Soviet Union lacks a strategic air force and poses no threat to the United States or Canada. It finds that the Soviets have about 100 heavy bombers that could reach Greenland and the Azores if Soviet ground forces captured forward bases for them in Norway and Spain, and about 100 medium bombers capable of striking Bear Island, Spitsbergen, Jan Mayen, Iceland, and the Faeroe Islands.
The U.S. Joint Intelligence Committee predicts that the Soviet Union probably will have atomic bombs by 1951 or 1952, and that the major target for such weapons would be American atomic bomb plants and major American cities.
October 14 – U.S. Air Force CaptainChuck Yeager takes the rocket-powered Bell X-1 past the speed of sound in the first controlled, supersonic, level flight. The flight, which achieves Mach 1.06, sets a new world air speed record of 807.2 mph (1,299 km/h). A few days later, the same aircraft sets a new world altitude record, reaching 21,372 meters (70,119 feet).
October 24 – United Airlines Flight 608, a DC-6 (NC37510) en route to Chicago from Los Angeles, catches fire and crashes while attempting an emergency landing at the Bryce Canyon, Utah, airport, killing all 52 people aboard. It is the first crash of a DC-6 and the second-deadliest air crash in U.S. history at the time.
October 26-November 7 – Rhulin A. Thomas makes the first solo coast-to-coast flight by a deaf pilot. (Calbraith Perry Rodgers was an earlier deaf pilot who flew coast-to-coast in 1911, but was supported by a team on the ground.)
November 2 – With Howard Hughes at the controls, the Hughes H-4 Hercules, also known as the "Spruce Goose," makes its first flight, traveling at 135 mph (217 km/hr) for about a mile (1.6 km) at an altitude of 70 feet (21 meters) over Long Beach Harbor in California with 32 people on board. Both the largest flying boat and the aircraft with the largest wingspan (319 feet 11 inches; 97.54 meters) ever built, it never flies again.
The U.S. Joint Chiefs of Staff note that the U.S. Air Force has 33 strategic bombers capable of dropping atomic bombs, and that this will rise to 120 bombers in November 1948. They also note that the number of atomic bomb assembly teams will rise to three by June 1948 and seven by July 1949; each bomb requires two days to assemble. They call for the production of 400 atomic bombs by January 1, 1953.