The WWII enigma surrounding the fate of a Finnish passenger plane shot down over the Baltic Sea by Soviet bombers appears to be resolved more than 80 years later.

The plane, carrying American and French diplomatic couriers in June 1940, was downed mere days before the Baltic states were annexed by Moscow. All nine people onboard, including the two-member Finnish crew and seven passengers — comprised of an American diplomat, two French nationals, two Germans, a Swede, and a dual Estonian-Finnish national — perished.

An Estonian diving and salvage team reported this week that well-preserved parts and wreckage of the Junkers Ju 52 plane operated by Finnish airline Aero (now Finnair) were located off Keri island near Estonia’s capital, Tallinn, at a depth of 70 meters (230 feet).

"Essentially, we began anew. We adopted an entirely different approach to the search,” explained Kaido Peremees, spokesperson for the Estonian diving and underwater survey company Tuukritoode OU, regarding the successful discovery.

The civilian plane, named Kaleva, was shot down on June 14, 1940, just three months after Finland signed a peace treaty with Moscow following the 1939-40 Winter War.

The news of the plane’s downing shocked and angered Helsinki officials, who were informed that two Soviet DB-3 bombers had attacked the plane 10 minutes after departing from Tallinn’s Ulemiste airport.

"It was extraordinary for a passenger plane to be shot down during peacetime on a routine flight,” noted Finnish aviation historian Carl-Fredrik Geust, who has investigated the Kaleva incident since the 1980s.

For years, Finland remained officially silent about the plane’s destruction, publicly calling it a “mysterious crash” over the Baltic Sea to avoid antagonizing Moscow.

Despite extensive documentation through books, research, and TV documentaries, this 84-year-old mystery has continued to fascinate Finns. The case is a pivotal chapter in the Nordic country’s intricate WWII history, highlighting its turbulent relations with Moscow.

Crucially, the downing of the plane occurred just days before Joseph Stalin’s Soviet Union began annexing the three Baltic states, altering the fate of Estonia, Latvia, and Lithuania for the next half-century. They regained independence in 1991.

Retrieval by Soviet Submarine

On June 17, 1940, the USSR occupied Estonia, and Kaleva’s ill-fated journey became the last flight from Tallinn, despite the Soviets already enforcing a strict transport embargo around the Estonian capital.

American diplomat Henry W. Antheil Jr., 27, was aboard the plane during its fall. He was on an urgent mission evacuating sensitive diplomatic documents from US missions in Tallinn and Riga, Latvia, due to the impending Soviet takeover.

Kaleva carried 227kg (500 pounds) of diplomatic mail, including Antheil’s pouches and material from two French couriers, Paul Longuet and Frederic Marty.

Estonian fishermen and the Keri lighthouse operator later told Finnish media that a Soviet submarine surfaced near Kaleva’s crash site and retrieved floating debris, including document pouches collected by fishermen.

This sparked conspiracy theories about the pouches’ contents and Moscow’s motives for downing the plane. The exact reason for the decision to shoot down a civilian Finnish plane during peacetime remains unclear.

"There has been much speculation about the plane’s cargo over the years,” Geust said. “Was Moscow trying to stop sensitive documents from leaving Estonia?" He suggested, however, that it might simply have been a mistake by the Soviet bomber pilots.

Many attempts to find the Kaleva wreckage have been made since Estonia regained independence over three decades ago, but none succeeded.

"The wreckage is in fragments, and the seabed is challenging, with rock formations, valleys, and hills. It’s easy to overlook small parts," Peremees said. “Technology has advanced significantly. Nonetheless, even with good tech, luck plays a role.”

Recent videos from underwater robots operated by Peremees’ company revealed clear images of the Junkers’ landing gear, one engine, and parts of the wings.

Jaakko Schildt, Finnair’s chief operations officer, called Kaleva’s downing “a tragic and deeply sorrowful event for the young airline”.

"Locating the wreckage of Kaleva provides some closure, although it cannot return the lives lost,” Schildt remarked. “The interest in finding Kaleva in the Baltic highlights this tragic event’s significance in regional aviation history.”