A number of airlines have suspended flights to and from Ukraine - however, Ryanair and Wizz Air will continue their operations.
Air France, Germany's Lufthansa, Dutch carrier KLM, and Scandinavian company SAS have stopped flights following the latest Russian action in Ukraine.
Latvian airline airBaltic has also halted its overnight flights to and from Ukraine.
READ MORE: Boris Johnson leads emergency meeting as Russian tanks roll into Ukraine
On Monday, the Kremlin ordered troops into two breakaway regions of eastern Ukraine, allegedly to carry out "peacekeeping" duties.
The dramatic escalation came after Mr Putin recognised the Donetsk and Luhansk regions in the Donbas as independent states.
However, Wizz Air has said it will continue to operate flights between the UK and Ukraine despite Russia's involvement.
The Hungarian airline connects Luton Airport with Kyiv and Lviv.
It runs three return flights per week on both routes.
A spokeswoman said: "Wizz Air continues to closely monitor the situation in Ukraine.
"Currently, we have not made any changes to our schedule and all of our flights to/from Ukraine continue to operate as normal.
"All passengers with booked flights to and from Ukraine are advised to regularly check their mailboxes for further information about booked flights."
Ryanair and Ukraine International Airlines also continue to operate flights between the UK and Ukraine.
Neither airline has announced any changes to those schedules.
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