Antheil was carrying several diplomatic pouches from the U.S. legations in Tallinn and Riga. Soviet troops had already been based in Estonia since October 18, 1939, as a result of the secret protocol to the Molotov–Ribbentrop Pact signed between the Soviet Union and Nazi Germany. Some Estonian researchers believe that Antheil's diplomatic pouches included secret information detailing the Soviet Union's future plans for the Baltic region that the Estonian General Staff had turned over to an unidentified U.S. government official earlier that same day. Back in the United States, the news of the Soviet blockade and the loss of the Aero Flight 1631 were overshadowed by a much bigger story that broke on the other side of Europe on June 14: the German occupation of Paris.