After you kill the Queen's escort, the bombers (presumably) come into the sector, as the ship count increases, but the bombers are usually out of radar range, invisible, and cannot find you or the queen. I tried waiting 20 minutes circling the queen and they never show up, this is confirmed by others.

Yep. I had the same result back when I took that mission. Sadly, I've used all three of my attempts -twice with no bombers showing up. The first time, they showed up and I died in the splash damages as the queen blew up.

they show up you are just to spaced out and unfortunately where to spawn them is not a choice of the mission editor so they spawn in the center of the sector where you started