system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] During the Death Star's trench run, why didn't the X-wings close their S-foils to increase maximum speed, so they could evade Vader's tie fighter?

The only thing the X-wings couldn't do is fire, but they could do this in the very last moment by opening their S-foils and fire the proton torpedoes.
gpt
They wanted to be able to pull up and get out of the trench at the last second instead of kamikazeing into the trench wall at the end of the run. This was also to ensure that one fighter could do repeated runs, which one did, should the computer miss and the bombs impact on the surface of the wall. Going in full throttle with the sfoils locked in attack position was the absolute fastest they could do it like this and even Luke was pushing it trying the run that fast. Unlocking at the last second to fire wouldn't give the fighters time enough to decelerate and get out of the trench with how fast they'd need to be going to out run Vaders tie fighter's blaster range.