Do you know anything more about this?
The Russian air force grounded its entire fleet of Sukhoi-27 fighter jets on Thursday after a fatal crash near Moscow which aviation sources told Russian agencies looked like the result of some kind of technical failure.
http://www.businessinsider.com/russia-grounds-fleet-of-sukhoi-27-fighter-jets-2016-6
Nothing new! This happens every six months to their fleets of SU-27s, Mig-29s, Mig-31s and SU-24s.