After hearing multiple speculations of how this accident happened we can be 95% sure the following was the case.
After the final split, the leading aircraft (nr.18 ) together with slot (nr.01) flew east for rejoin and head back to Kubinka, Russian Knights home base. The left wing, Vitaly V. Melnik (nr.14, also flying east after split) was the first jet to rejoin the formation.
This rejoin is what went wrong. Left wing, sliding in from a higher altitude, miscalculated the leaders airspeed and overshot the formation. During overshooting, Vitaly V. Melnik probably lost visual and hit the leading aircraft with the engines. The nose of the leading aircraft was severely damaged.
The leading aircraft was a double seater. In the front seat flew Commander Igor Tkachenko and in the backseat, navigator Igor Antonovich Kurilenko. Kurilenko immediately ejected after the collision initiating both front and back seat ejection sequence.
Horrifying is that Tkachenko's parachute cought fire during the eject. Though, looking closely at the pictures we can assume that Igor Tkachenko was already dead from the impact.
The engines of left wing, nr.14 cought fire and Vitaly V. Melnik ejected a few moments later.
Jet Nr.14 after ejection
Crash site Nr.14
Crash Site Nr.18
May Igor Tkachenko rest in peace......
RIP
