What happened to Russia's Air Force? U.S. officials, experts stumped

FILE PHOTO: Russian Sukhoi Su-35 jet fighters fire missiles during the Aviadarts competition, as part of the International Army Games 2021, at the Dubrovichi range outside Ryazan, Russia August 27, 2021. REUTERS/Maxim Shemetov/File Photo

WASHINGTON (Reuters) -Before Russia's invasion of Ukraine, U.S. intelligence had predicted a blistering assault by Moscow that would quickly mobilize the vast Russian air power that its military assembled in order to dominate Ukraine's skies.

But the first six days have confounded those expectations and instead seen Moscow act far more delicately with its air power, so much so that U.S. officials can't exactly explain what's driving Russia's apparent risk-averse behavior.