Kaleva was a civilian Junkers Ju 52 passenger airplane belonging to the Finnish carrier Aero O/Y.

[2] On 14 June 1940, Kaleva had already made the scheduled stops along the route Stockholm-Turku-Helsinki-Tallinn and, as Aero Flight 1631 on its first return leg, was due to fly from Tallinn (Ülemiste) to Helsinki (Malmi) airport.

A few minutes after taking off from Tallinn, the airliner was joined at close range by two Soviet Ilyushin DB-3 (DB-3T) torpedo bombers.

The Soviet aircraft opened fire with their machine guns and lethally damaged Kaleva, causing it to crash into water a few kilometers northeast of the Estonian Keri island in the Gulf of Finland.

The attack occurred amidst Soviet preparations for the full-scale invasion and occupation of Estonia by the USSR on 16–17 June 1940, just two days after the Kaleva incident.

The commander of Shch-301 G. Goldberg's report on the incident held in the Russian State Naval Archives starts with the notice of a Finnish airplane on its way from Tallinn to Helsinki on 14 June 1940 at 15.05 PM.

At 15.06 PM, the Finnish airplane caught fire and fell into the sea, 5.8 miles (9.3 km) from the submarine.

[5] Captain A. Matveyev's report states that on board the Shch-301 noticed an airplane crash on 14 June 1940 at 15.06 on 5.8 miles (9.3 km) distance from the submarine.

The items included about 100 kg (220 lb) of diplomatic mail, and valuables and currencies including: 1) Two golden medals, 2) Finnish mark 2,000, 3) 10,000 Romanian leu, 4) 13,500 French franc, 5) 100 Yugoslav dinar, 6) Italian lira 90, 7) United States dollar 75, 8) 521 Soviet roubles, 9) 10 Estonian kroons.

A well-known navigator of Soviet long-range aviation, Lt General Pyotr Khokhlov, in his memoirs "Above Three Seas" (1988)[7] described his participation in the incident: ...after having approached the aircraft Ju-52 without any identification marks, I opened the astrohatch of my cabin, rose, and showed the pilot by hand to turn the vehicle toward the (Tallinn) aerodrome.

...In parts of fuselage that were raised from the bottom of the gulf not only were plenty of material valuables discovered but also many documents with state secrets... We understood why the crew of the Ju-52 refused to comply with the demand to return to the aerodrome: they would have had to account for the espionage...

The plane was piloted by Captain Bo von Willebrand, and Tauno Launis was the wireless operator.