Ukraine

Interestingly:

The safe passage of these vessels is being ensured by the American anti-ship patrol aircraft Boeing P-8 Poseidon, which is refuelled in the Romanian sky. Additionally, the Forte12 RQ-4 reconnaissance drone provides valuable information about the maritime situation.

This is absolutely a “fuck around and you’ll find out” play. There is a P-8 officially advertising it’s presence as a protective measure. But I would honestly be shocked if there’s not a LOT more NATO hardware (likely mostly stealth, plus AWACS and ELINT) in the area as backup.