A psychological blow may be the biggest impact of Ukraine’s Spiderweb operation, say experts.

Russia’s increased sense of vulnerability may be the most important result of a recent large-scale Ukrainian drone attack named Operation Spiderweb, experts tell Al Jazeera.

The operation destroyed as much as a third of Russia’s strategic bomber fleet on the tarmac of four airfields deep inside Russia on June 1.

Days later, Russia started to build shelters for its bombers and relocate them.

An open source intelligence (OSINT) researcher nicknamed Def Mon posted time-lapse satellite photographs on social media showing major excavations at the Kirovskoe airfield in annexed Crimea as well as in Sevastopol, Gvardiyskoye and Saki, where Russia was constructing shelters for military aircraft.