The first movie, Blackout's tail number was 4500x. In RotF, Ironhide had the model number 4500. In DotM, a jet plane in the background had the tail number 4500x. Not too sure about the second instance and there might be more. I was curious about this because it doesn't come off as a subliminal message to buy a GMC truck. Anyone else have an idea of what this was about, or is this like the "Bad Boys II" poster in the second movie?