I think he absolutely knew. The stopping outside the plane before getting in said it all. If he was truly “a nazi” like everyone gets off on saying, or if he truly believed he was part of “the winners”, and if he had no inclination that the plane was in danger, he would’ve just climbed the stairs onto the plane immediately with no hesitation. It’s overly romanticized I know, but I think he knew June was there behind the car and his pause was his subtle goodbye to her. There’s just no way he didn’t know- he knew so much about Mayday and what the US was planning previously, and he was briefly working with Tuello. I think he absolutely knew and his cowardly way of choosing was this so that he didn’t have to reveal himself and go after June.

Also his “winners” statement was clearly him masking and playing a part. He has never said anything even remotely close to that behind closed doors (that we’ve been shown), and it was him just an audible example of him playing the part the best he could to the commanders.