There's an American one (a Rivet Joint, which for those without the lingo are recon-gathering and largely signals intelligence; basically, listening posts) flying back and forth over Romania near Moldova right now too.
And if you can find FORTE10 over Romania, that's a USAF recon drone.
For the tankers, it looks like the UK is handling the northern sector (see RRR9140 over Lithuania now) and the USAF the southern part (LAGR callsigns that loiter over Romania).
A few more unidentified airframes flying under US military callsigns are in eastern Poland too, plus the two DUKE callsigns (which are Black Hawk helicopters) that seem to have been up there during the day pretty consistently.
Also note RSD088, a Tu-204 en route from Moscow flying west over Belarus. That'll be the Russian negotiation delegation coming in.