A US Air Force Boeing RC-135U reconnaissance plane flew over the Black Sea and changed course not far from the Russian city of Sochi, heading towards Europe, according to data from the Flightradar24 website.
According to the route, the plane took off from its base in Mildenhall, UK. It then passed through the Netherlands, Germany, the Czech Republic, Slovakia, Hungary and Romania.
The plane flew over the Black Sea past Crimea and turned west on its way to Sochi.
At 2:55 a.m. Bulgarian time on Tuesday, the plane crossed the border between the Czech Republic and Germany and continued its return flight over German territory.