In the early 1950s, US and British aircraft carried out reconnaissance operations over the western Soviet Union via Danish, Norwegian and Swedish airspace. The Swedish Defence Staff noted that US aircraft went in and out of Soviet airspace over the Baltic republics. British aircraft dropped agents in the Baltic republics. On the evening of 28 April 1954, several US aircraft entered Swedish and Danish airspace. The aircraft were observed at several places along the Swedish west coast and in southern Sweden as a whole. During the night, some aircraft patrolled outside Göteborg, Malmö and Copenhagen, while others, after having been refuelled by the former, went in over Sweden, the Baltic Sea and deep into the western Soviet Union including Novgorod, Kalinin, Smolensk and Kiev. The Soviet air defences were, at the time, not able to intercept the US aircraft. When the latter aircraft returned to the Malmö-Copenhagen area, they were once again refuelled, and after that they all left, probably for the US Strategic Air Command’s bases in the UK. A week after this incident, the Swedish Defence Staff wrote in a classified report that the aircraft were either American or British. The Danish Minister of Defence, Rasmus Hansen, stated at a confidential party leader meeting that he could not exclude that the aircraft were American, but this should not be reported to the Parliament or to the public.1