I also have no experience with UMs. That said OP if if I was doing it I would only send a UM on DL or UA, since no one flys non-stop TLV-ORD. LY will mean having to change terminals and carriers.Id rather it be 1 carrier in case something should hit the fan and the same term or at least by it being the same carrier less of a chance of a botched pass-off. I wouldnt use AC or any European carrier since if something hits the fan she will be stuck outside the US . I believe that the non-US Carriers will look after a UM much better, but dont want to deal with the kid being stuck in ZRH,VIE,FRA,LHR etc and having to Overnight due to missing the connecti8ng flight. Out of EWR and JFK miss 1 flights there are others Out ofDL and UA Id prefer UA since DL probably ha slimited flights JFK-ORD while UA will have many