Kaleva was a Junkers Ju 52 transport plane, belonging to the Finnish carrier Aero O/Y. The aircraft was shot down by two Soviet Ilyushin DB-3 bombers on June 14 1940, while en route from Tallinn to Helsinki. A few minutes after taking off in Tallinn, Kaleva was joined at close range by two Soviet DB-3T bomber aircraft. The bombers opened fire with their machine guns and badly damaged Kaleva, making it crash on its left side into the water a few kilometers northeast of Keri lighthouse. All nine passengers and crew members on board were killed.

Estonian fishermen had witnessed the attack and crash of the plane. Shortly after the crash the Soviet submarine Shch-301 (Щ-301) surfaced and inspected the fishing boats. After confiscating items taken from the wreck by the fishermen, the Soviets picked up diplomatic mail from the wreck and the sea. The future top-scoring Finnish pilot Ilmari Juutilainen was sent to inspect the crash site. After the Soviets spotted the Finnish airplane, the submarine hid its flag.

At the time of the incident Finland was not at war with the Soviet Union. The attack was probably part of the Soviet preparations for the full-scale occupation of Estonia, which took place two days after the "Kaleva" incident, on 16 June 1940. The occupation was preceded for several days by a Soviet air and naval blockade, which included preventing diplomatic mail from being sent abroad from Estonia. The passengers on the last flight of "Kaleva" included two German businessmen, two French embassy couriers, one Swede, one American courier and an Estonian woman. The French couriers had over 120 kilograms of diplomatic mail in the plane. The American courier was reportedly transporting the U.S. military codes to safety from Estonia.

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

The Government of Finland did not send any complaints or questions to the Soviets out of fear of hostile Soviet response, and the true reason for the crash was hidden from the public. This was due to the heavy pressure put upon Finland during the Interim Peace by the Soviets. After the outbreak of the Continuation War, the incident was described in detail by the government.