There are multiple conflicting sources of information that may influence such decisions. The overwhelming evidence is in favor of a possibility that a further invasion by the Russian regime may take place.
Russia under the current authoritarian rule of President Putin has already invaded Ukrainian territory both directly (Crimea) and indirectly, through the actions of the puppet regime (Donbass). Putin has invaded Georgia and Moldova in the past. Russia has made operations of the Azov sea (essentially converted into the Russian inner lake) and Black sea Ukrainian ports difficult if not impossible. This is in essence a naval blockade, without announcing it as such.
The military, diplomatic and political analysts (see below, but there are more examples that I can add) agree that the continuation of the Russian invasion cannot be ruled out. It follows from common sense that flight insurance for commercial flights over a possible military zone may be prohibitively costly. Hence, conversion of Ukraine into a no-flight zone for some operators.
And the recent memories of evacuation of the the US and pro-US civilians from Afghanistan in 2021 are alive and well. This suggests that the current ruling elites in many countries have little appetite for a repeat of such a disaster. Hence the thinning out or the outright evacuation of the diplomatic staff.
“In the event of a military threat from Russia, the decision to close
Ukraine’s airspace will be made immediately by the top military
leadership, taking into account the situation and risks,” Lt. Col.
Yuriy Ignat, head of the Ukrainian air force’s Public Relations
Service, told Coffee or Die Magazine in an exclusive interview.
“The air force of the armed forces of Ukraine monitors the airspace
over the territory of Ukraine and beyond on the territory of
neighboring states,” Ignat said, adding that Ukrainian air force
commanders “work in close cooperation” with civilian air traffic
control to prevent the targeting of nonmilitary aircraft such as
“Passenger planes will be identified and cannot be considered Russian
combat military aircraft,” Ignat said. “However, Russia’s provocative
actions in the airspace cannot be ruled out. Such scenarios are also
calculated and modeled by the Ukrainian military.”
(With Ukraine’s Air Defenses Ready for Russian Attack, Civilian Aircraft Cautiously Keep Flying. By Nolan Peterson. Coffee or Die. December 28, 2021: https://coffeeordie.com/ukraine-air-defenses/ )
The second phase of Russia’s highly anticipated bilateral military
exercise with Belarus, called Union Courage ’22, kicked off on
February 10. But much more than reaffirming the relationship between
the two countries, it is a useful cover for the deployment of Russian
high-end military equipment and an opportunity to rehearse missions
applicable to a large-scale Russian invasion of Ukraine.
While imperfect, the proliferation of commercial satellite imagery and
hand-held photos and video have provided a surprisingly thorough look
at Russia’s military build-up. Its Ministry of Defense (MoD) has also
provided insights into the types of missions these joint forces have
engaged in—which allows experts to extrapolate the missions the
Kremlin believes are important and to assess how they intend to
execute combined arms operations in the event of a further invasion of
Although the execution phase of the exercise has only just begun, there is already plenty to learn from the types of forces deployed, the actions they have conducted so far, and the subjects Russia has chosen to publicize. Based on these observations, it is clear that Russia is focusing on air superiority, close air support, long-range fires, intelligence collection, and combat sustainment.
The bottom line
Russia has already deployed the forces necessary to initiate a large-scale invasion of Ukraine. It is using the Union Courage exercise to posture and prepare those forces to conduct offensive operations against Ukraine, should they be directed to invade. Based on observed deployments and training events, it is apparent that in the event of a further invasion, Russia intends to rapidly establish air superiority over Ukraine and will initiate its mechanized offensive with precision long-range fire (both from the ground and from aircraft). And it will be prepared to support that ground offensive with overwhelming support from ground-attack aircraft.
( Russia’s joint exercise with Belarus reveals what a Ukraine invasion would look like. By Tyson Wetzel. February 11, 2022. New Atlanticist: https://www.atlanticcouncil.org/blogs/new-atlanticist/russias-joint-exercise-with-belarus-reveals-what-a-ukraine-invasion-would-look-like/ )
Search for these, sort by most recent first:
Ambassador Michael McFaul (Professor at Stanford): https://www.youtube.com/results?search_query=michael+mcfaul
Vitaly Portnikov (political analyst), in Ukrainian and Russian languages: https://www.youtube.com/c/portnikov
Viktor Nebozhenko (political analyst), in Ukrainian and Russian languages: https://www.youtube.com/results?search_query=%D0%BD%D0%B5%D0%B1%D0%BE%D0%B6%D0%B5%D0%BD%D0%BA%D0%BE+%D0%B2%D0%B8%D0%BA%D1%82%D0%BE%D1%80
[Edit Feb 19 2022]
Putin recently announced on the state-controlled TV that Ukraine has engaged in "genocide" in Donbass (new!). This is a lie, & is also unprecedented. It begs the question: why wait, why not stop the "genocide" by intervening, militarily if needed, to protect the ethnic Russians + the 1000s of the newly minted Russian citizens in Donbass? Et voila, casus belli created! Need more? Putin introduced a near-blockade of civilian ports of Ukraine in the Azov & the Black seas (new!). And Putin-supported separatists shelled preschools and schools in Ukraine today, Feb 17, 2022 (new!).
Plus a wall of references here: