Been looking for this anime for at least a decade!

Here goes. It all started with a female pilot getting dressed for combat, then going into her fighter spacecraft and taking off. Epic air battle ensued, basically her and her collegues were vastly outnumbered but kept on fighting against lots of enemy spaceships.

Eventually, she was forced to land on the enemy planet, which was mostly desertic (and red?) except for a dome-shaped base. She entered the base and started exploring it. Not much light. Meanwhile, there were cutscenes featuring a giant robot spider waking up inside the base and crawling towards the pilot.

The short anime ended with the two facing each other, I think. Can’t remember if it was a music anime or an excerpt from a longer movie though.