Reference to the 51st Fighter Group
At the end of the movie, the B-17 pilots learn they're going to Berlin and that they were to be escorted by the 51st Fighter Group. They then ask specifically to be escorted by the 332nd instead.
It was a pretty smart thing to ask for. Even with the P-51 Mustang being the longest ranged fighter in the world at that time, if the 51st Fighter Group had been tasked for an escort mission to Berlin, they would've run out of gas somewhere over northern Afghanistan, because they were stationed in Kunming, China at the time!