 Putin prepares to bring Russia's Su-57s and numerous bomber jets to the war on Ukraine. Military intelligence leaked online last week indicated Ukrainian air defenses will be depleted by the end of May, which may embolden Russian President Vladimir Putin to bring reserved fighter jets to the front lines. Ukrainians are rapidly using up stores of munitions faster than allies can replenish them. At the current rate of use, the leaked documents say Ukrainian air defenses will be completely reduced by May 23, the New York Times reported. The veracity of the documents is still being investigated, though some versions circulating online have been edited. Business insider outlet previously reported, without increased military aid, which Ukrainian President Volodymyr Zelensky has repeatedly told allies should come in the form of F-16 jets, Russia may be emboldened to bring out bomber jets it has been saving from facing Ukrainian defenses that have so far destroyed 280 Russian planes. Fighting against a weakened Ukrainian air force, increased Russian firepower could change the course of the war. Russia has so far held back its most advanced jets, including its much touted Su-57 stealth fighter. From the front lines of the war over fears that they would be shot down, Business Insider previously reported.