Two U.S. officials told Reuters on June 4 that Ukraine struck as many as 20 Russian military aircraft during Operation Spiderweb, destroying around 10 of them. The claims stands in contrast with estimates made by Ukraine's security service (SBU) which claimed more than 40 aircraft were hit in the June 1 attack.

The audacious attacks on Russian airfields highlight the power of unconventional, asymmetric warfare — and the threat to U.S. strategic bases and ports, experts say.