Drones are “ubiquitous, because they are quite useful, and they're demonstrating that every day in Ukraine,” one analyst told NBC News.

The covert operation was described as one for the “history books” by Ukraine’s president. According to Ukrainian officials, nearly a third of Moscow’s strategic bomber fleet was destroyed or damaged with cheaply made drones sneaked into Russian territory in the span of a few hours on Sunday.

Russian aircraft were damaged but not destroyed in a June 1 attack by Ukraine, and they will be restored, Russian Deputy Foreign Minister Sergei Ryabkov said in an interview with the state news agency TASS.