Originally Posted by BlueLightning
I thought that it was because he still had the chance to fulfill the death wish he longed so much. For me, the close up is him pondering if he would choose to save himself.
Other posters had pointed out that perhaps he hadn't tested the autopilot, so there was still the chance that he couldn't make it, and he didn't want to give Selina a false hope.
My thoughts exactly. You can even say Bruce's expression was one of relief. Very, very nice moment.