Romeo Charlie: "Centre, this is Romeo Charlie checking in with you. Flight level 110."
ATC: "Roger Romeo Charlie, are you the one with the red stripe?"
Romeo Charlie: (exchanging puzzled looks in the cockpit) "er…negative. We are mostly white with blue stripes. We do have a sister company aircraft with a red stripe. Maybe you're thinking about that."
One minute later…
ATC: "Sorry Romeo Charlie. I was just having a bit of fun. From here you just look like a small greenish square."
Source: Flight International