The National Trophy, the Harmon Trophy presented to the outstanding aviator for the year in each of the 21 member countries of the International League of Aviators, is awarded for the last time, although the annual award of the Harmon Trophy to the world 's outstanding aviator, aviatrix (female aviator), and aeronaut (balloon or dirigible aviator or aviatrix) continues.
March 16–18 – Italian aircraft based on Majorca carry out a heavy, round-the-clock bombing of Barcelona, conducting seventeen air raids at three-hour intervals. Making no attempt to strike military targets specifically, they hit all parts of the city, killing about 1,300 people and injuring about 2,000.
March 22 – The Nationalist Aragon Offensive resumes. Bombing and strafing German, Italian, and Spanish Nationalist aircraft play a large role in terrorizing and routing Republican ground forces for the remainder of the offensive.
April 19 – The Aragon Offensive ends, with Spanish Nationalists having routed Republican forces and cut Republican-controlled Spain in two. Nationalist air superiority has proven decisive in their victory, and both the Germans supporting the Nationalists and the Soviets supporting the Republicans have learned a great deal about fighter support to infantry.
June 2 – Nationalist aircraft bombGranollers, Spain, a town without military significance, killing about 100 people. Most of the dead are women and children.
June 4 - S. T. Lowe wins Hatfield to Isle of Man air race flying a Gypsy Comper with a time of 2 hours 55 minutes 28 seconds, the fastest time of 16 international entrants of whom notable entrants were C. W. A. Scott and Giles Guthrie who came in 5th place.
In an Imperial Japanese Navy raid on a Nationalist Chinese airfield at Nanchang, three Japanese aircraft land on the field and their pilots disembark to shoot up Chinese personnel, barracks, and hangars and set Chinese aircraft on fire on foot before taking off and departing unscathed. The Japanese will use this attack technique on several future occasions.
July 5 – 400 aircraft support a Spanish Nationalist offensive in Valencia.
July 15 – A German Arado Ar 79training and touring aircraft sets an international solo speed record over a 1,000-km (621.4-statute mile) course for an aircraft of its class, averaging 229.04 km/hr (142.32 mph).
July 24 – Disaster strikes when a Colombian Air Force pilot performing an aerobatic display in a Curtiss Hawk IIbiplane fighter at a military review at Campo de Marte, Santa Ana, Usaquén, Colombia, disregards orders to remain above 500 feet (152 meters) and attempts to fly between the camp 's presidential grandstand and diplomatic grandstand. His wingtop strikes the diplomatic grandstand, and his aircraft careens into the presidential grandstand, destroying part of its roof, before crashing into a crowd of spectators on the ground between the two grandstands, bursting into flames and sliding through them before coming to a stop upside down. An estimated 50 to 75 people are killed, and another 100 people – including future President of ColombiaMisael Pastrana Borrero – are injured. Outgoing Colombian President Alfonso López Pumarejo and his successor Eduardo Santos are in the presidential grandstand but avoid injury.
July 25 – The Battle of the Ebro begins in Spain with a Republican offensive. Although Nationalist bombers attack bridges over the Ebro, Nationalist fighters are still deployed in Valencia and Spanish Republican fighter pilots trained in the Soviet Union gain local air superiority flying improved versions of the Polikarpov I-15 and I-16.
July 28 – After physicians at the Mayo Clinic design a molded latex device with an attached rubber "lung" to provide oxygen for people on flights above 10,000 feet (3,048 m), Northwest Airlines pilot Mal Freeburg flies a Douglas DC-3 carrying the physicians, airline employees, and his wife, with all aboard using the new device. The test is a success, and the flight marks the first use of a modern American aviation oxygen mask.
By the beginning of August, Nationalist fighters appear in sufficient numbers to establish Nationalist air superiority over the battlefield in the Battle of the Ebro. Inadequate Republican antiaircraft artillery, poor management of Republican fighters, the death of many Republican pilots, and the withdrawal of many of the best Soviet pilots from Spain all allow Nationalist aircraft to operate largely unchallenged. Up to 200 Nationalist aircraft circle over the battlefield as Nationalist forces begin a counteroffensive, shooting down many Republican fighters and dropping an average of 10,000 pounds (4,536 kg) of bombs per day into September. Small targets prove difficult for Nationalist aircraft to hit, with over 500 bombs needed to destroy a single Republican pontoon bridge in one instance.
September 30 – A senior French general tells the British military attaché in Paris that in the event of a war with Germany "French cities would be laid in ruins ... They had no means of defense," and adds that France was paying the price for having neglected the French Air Force for years.
November 18 – The Battle of the Ebro ends with Spanish Nationalists retaking all territory captured by the Republicans. The Spanish Republican Air Force has lost between 150 and 170 aircraft since the battle began on July 25, and the Nationalists also have lost many planes.
November 26 – France lays the keel of its second aircraft carrier, Joffre, intended as the first non-experimental French carrier. Joffre 's construction will be abandoned in June 1940, and she will never be launched.
National Aviation, the Spanish Nationalist air force, has 500 aircraft, enough to ensure it air superiority in the Spanish Civil War.
December 5 – At a meeting of the French Permanent Committee on National Defense, Chief of Staff for National Defense General Maurice Gamelin advocates that France immediately order 1,000 military planes from the United States. The committee approves his proposal.
December 30 – The Italian Piaggio P.23R sets two new world records for payload and speed over distance, carrying a payload of 5,000 kg (11,023 lbs) over a distance of 1,000 km (621 miles) and over a distance of 2,000 km (1,242 miles) at an average speed for each distance of 404 km/hr (251 mph).