F/A-18 Hornet. Photograph:: The Finnish Air Force

HELSINKI—Did you hear a rumble in the sky somewhere over Helsinki? The reason has a traditional Finnish name: Ritva 21.

Ritva 21, according to the Finnish Defence Forces, is a partial exercise led by the Navy Command held May 26—June 2 in the Gulf of Finland and the Archipelago Sea area and on the coastal areas of Uusimaa.

Parts of the exercise also take place in Satakunta, Varsinais-Suomi, Pirkanmaa and Uusimaa.

Because of the coronavirus pandemic, the Defence Forces’ main war exercise in spring 2021 has been implemented as sub-exercises across Finland.

And Ritva 21 is one of them.