[mapt]

Both Poland and Iran have lost regionally inconvenient heads of state to crashes in fog.

I think there is concern there with undiagnosable crashes, but also a more pronounced concern with hijacking. If you have access to the plane you can just plant a bomb. With this you could capture the plane for hostage or turn it into a missile.

[Hypomixolydian]

In case of Polish crash, according to the official Polish government report, the Russian involvement is more than possible: https://www.smolenskcrashnews.com/pdf/2022-smolensk-crash-re...