The time of flight to the target should be two or three seconds.Again, the emphasis is mine.
All the Su-15 pilot could do now was watch, wait and get out of the way. He pulled back gently on the control column to gain a bit of height, perhaps two hundred or three hundred feet. Best to avoid any debris, because once those rockets hit the target would disintegrate. It would leave a trail of fragments, as pieces peeled off the aircraft like feathers from a bird. If the Su-15 hit even a small bit of flying metal or other material it, too, could be destroyed. So he would avoid that danger by flying a little higher while keeping an eye on the target’s running lights.
It should go any moment now!
In a split second the telltale impact flames burst into a massive, billowing orange ball of fire sliced by black streaks of burning fuel. From behind and slightly above, the Soviet pilot could see the fuselage of the huge target aircraft as it was swallowed by the sphere of fire while being ripped open by the force of the simultaneous blasts of the pair of rockets…
— Richard Rohmer, Massacre 747
I'd like to add that those two to three seconds are the longest two or three seconds in Canadian Literature.