It could be an anomaly, if I remember right, the P-36 wasn't originally released as a flyable aircraft in the IL-2 series. An errent string of code could trigger objects or events under the right conditions.
In MechWarrior 3, there was a small "box" that we found near the border of a certain map, that only occurred when there was one or two players and only at certain times. There was no explanation as to why it showed up, and after a while, it would go away.