Turkish Air from the states, well organized and efficient; zero issues including for the change of planes in Istanbul (mask requirement enforced well on flight and in airports).
CDC card accepted at Kyiv Airport without a second look (but don't forget $6 mandatory COVID insurance).
[lessening requirements: when I planned the trip a covid test was required. No longer. When the rule changed the new rule said the vaccine card had to have a lot of info not on the CDC card so I created a notarized document with a photo of the card and the missing info. No longer required]
Ukrainian people welcoming tourists and enjoying the money and jobs returning.
In-country flight to Odesa, no questions, no issues.
Everything fully open, remaining COVID restriction to wear a mask inside about 75% followed.
Country 1 - Ukraine
https://community.ricksteves.com/travel-forum/general-europe/country-one-entering-ukraine
Country 2 - Turkey
https://community.ricksteves.com/travel-forum/general-europe/country-two-turkey
Country 3 - Croatia
https://community.ricksteves.com/travel-forum/general-europe/country-three-croatia
Country 4 - Bosnia & Herzegovina
https://community.ricksteves.com/travel-forum/general-europe/country-four-bosnia-herzegovina
Country 5 - Montenegro
https://community.ricksteves.com/travel-forum/general-europe/country-four-montenegro