Ace Combat Fan just posed a video showing an unwinnable softlock for doing the mission 20 tunnel run too fast. Figured this should be posted here so people know there is a limit to going fast. That said, huge props to anyone who can actually pull this off, that takes some steady and precise flying.

Long and short of it, make sure Count gets hit while you're in the tunnel segment or the drone doesn't spawn and you can't climb high enough to escape.

As the WR holder for both Any% and DLC category on the M20 Tunnel Run, I ran into this a lot.

This is the current theory for the reason this happens (though the DLC craft somewhat disproves it):

There are a number of dialogue and spawn triggers in the tunnel. These aren't always there and spawn one after another. If you fly too fast you'll go through said triggers before they appear.

You'll notice that if you go too fast, the ADF-11 won't spawn in the last section of the tunnel. If this happens, you know that you've got the softlock.

If you look at my runs here you'll see that the ADF-11 spawns really late, and I got lucky with both runs.

I also noticed that if you use the Darkstar, which is faster than the MiG-31, this softlock never occurs, which is weird.