Some Soviet pilots and advisors were killed in action in No. Vietnam including during the raid on Son Tay POW camp. I was just leaving a journalism visit/fact-finding mission in S. Vietnam and Cambodia, airborne to be exact, when that raid took place.
A few may have been killed over Laos.
Just a few interesting sidebar comments.
Did they ever pin down for sure who those up to 200 guys they killed were, at the time they didn’t know if they were Chinese or Russians or what, just that they were taller.