So far I don't think there's any need to be stopping passenger flights in and out of Ukraine and to do so would be knee-jerk and damaging to the Ukranian economy which is no doubt already struggling just like everywhere else in the world.
I don't think we will see bullets fly. War will be avoided at all costs. This one is a case of 'stay calm and wait it out' and hope the diplomats know what they're doing.