Why are two Soviet air leaders disappearing?

[M60A3TTS]

Bitter End Scenario

The commanders of 2nd and 4th BAK are disappearing on turn 10 when their HQ disband.

Sudets, V air rating 6
Smirnov, K. air rating 5

It's kind of an issue because let's face it, the Soviets aren't exactly blessed with good leaders.

If you replace them prior to turn 10, they simply vanish from the leader screen. Similarly, you can't have them replace another air leader as they do not appear as an option.

[Denniss]

They will reappear in 1942 when they historically assumed command of Army-level HQs