– Russia Is Modernizing Its Fleet of MiG-31 Interceptor Jets (Russia Insider, April 15, 2015):
The first batch of 24 modernized MiG-31 BM fighter jets enters service
The first 24 modernized MiG-31BM fighter jets have been delivered to the Russian Armed Forces. Deputy Defense Minister Yuri Borisov said more than ten aircraft will be delivered to troops ever year.
“After completing the modernization of the MiG-31, we expect that military forces will have more than 130 updated, outstanding aircraft with key technical parameters available for use,” said Yuri Borisov. According to him, about 12-13 aircraft undergo modernization per year.