Today in Miami, I saw a Santa Barbara Airlines AC (sorry, didn't pay attention to type). My first (and correct thought) was that it isn't a US airline. That is confirmed by their web site. So why did it have an "Nxxxx" tail registration? If they lease the plane from a US owner is that what would explain it? Maybe this isn't uncommon, but I don't recall seeing an obvious country of operation/aircraft registration mismatch.