The Belarus plane hijack is a small reminder why it's generally not a good idea to let governments know who is going to where. I'm not sure why governments that like to think of themselves as democratic don't see the risks.
-- Alexander Bochmann https://mastodon.infra.de/@galaxis/106285985254850170
I'd made a similar point following the assassination of Kim Jung-nam in 2017:
Travel and hospitality databases are widely accessible and shared amongst a tremendous number of organisations. State intelligence organisations might readily have access through their own state-run airline, or through private operations or plants within same. Similarly for terrorist, narco-criminal, money-laundering, or other organisations. Financial, banking, and payment-processing systems, only slightly less so. A P.I. license or position on a fraud or abuse desk at a major online retailer, or any skip-tracing agency, can have access to such information.
https://old.reddit.com/r/dredmorbius/comments/5ud243/data_ar...
What is your threat model?
Note that your own threat model may not include possibilities which put others at risk.
(In fairness, it appear that Protasevich was followed onto the plane itself, suggesting that in-flight availability of manifests played little role. The question of what pre-flight intelligence methods were employed remains open.)