My memory goes back to the problems in Yugoslavia. From what i understood they did not shut their airspace, some airlines decided not to overfly (their own assessment) but certainly routeing eastbound was forbidden (i think after an assessment by NATO in conjunction with eurocontrol) very quickly.
If my memory serves me correctly, again after assessment by NATO, we were able to overfly westbound above 370.
Why were these types of assessments not made for Ukraine?