Below data is from flightradar,
USN RQ-4B/D used to take off from Sigonella AB, near Catania (Sicily, Italy) every day, fly over Greece, Bulgaria, Romania and circle 8+ hours over the center of Black Sea.
KC-135 of RAF would take off daily from Brize Norton (UK), or USAF KC-135 from Ramstein AB (Germany), fly to Constanta, Romania, circle for a bit (I guess refuelling), and fly back.
Since the drone interception by Russia, these events are no longer occurring, according to flightradar. Or they may have just hidden the call signs.
Other than that, there are daily flights of USAF C-17A from Virginia/North Carolina to 1) Rota AB (southern Spain), 2) Brize Norton. From here, they go to Ramstein, Sigonella or Rzeszow (eastern Poland, near Lviv Ukraine).
When the Nordstream was attacked, there was a lot of USAF/USN activity in the region, originating from Ramstein, involving E2, E3, E7, E11. That has stopped now.
It appears, US + NATO is providing daily electronic coverage (and interference) over Ukranian airspace from beyond its borders. I reckon, Russian Black Sea fleet is somewhat hampered in its operations due to NATO ELINT provided to Ukraine.