That means it has to have been attacked from ahead as chasing a high flying a/c going at 9 miles a minute would soon exhaust its fuel supplies.
Google is your friend (or Wiki is)
Buk missile system - Wikipedia, the free encyclopedia
Depending on the model, these missiles can travel at Mach 2.5 to Mach 4. One video report says that it could hit the target in 40 seconds.
I don't think chasing is much of an issue.