[justsomehnguy]

With all their operations in (and supporting) Syria I would doubt the number. It is not the amount of USAF pilots, but should be more than that.

[RobertMiller]

That number supposedly comes from official Russian sources. I say supposedly because I don't understand Russian and have to trust western sources about this, but these numbers have been widely disseminated for years and seem to be broadly treated as credible.