Even if a Ukraine fighter jet hid in the shadow of a commercial aircraft I fail to see that as a justification or an "exigent circumstance" as excuse or justification to shoot down a civilian aircraft.

"Sorry, we killed 288 people by mistake ... OOPs"

They could have waited until they had a clear shot at the military fighter aircraft -- "they (to be determined exactly who)" fucked up and 288 civilians died from their act no matter how you try to spin it.