This category relies on using the helicopters to set up the flying glitch not only in area 1, but also in 3 and 4. In areas 3 and 4, you need to break the glitch state to fight the level boss, which is the only known way to clear these areas. The flying glitch can be broken by leaving the helicopter at the same time as the helicopter explodes. This can be done by self-exploding the helicopter (fire a rocket right as you exit it) or by exiting the helicopter just as you approach a mine, a kamikaze soldier etc.

Below are shown the parts that will be different from the no-death route and some faster and riskier strats. The latter can be justified by the fact that this category is significantly less RNG-dependent to complete than a no-death run.

Area by area description

Area 3

Foot2 and 3 - https://www.youtube.com/watch?v=bfEbdPvBjzY
Skipping the tank and going on the left side saves around 4.5 seconds. The first section that could instead have been done in the tank is definitely not without risk on foot though.
A heart is required before the helicopter, so the one on the way on the left side is well located. However, there is also another heart later on that is also almost on the way if you prefer to stick to the right side.

Foot4 - https://www.youtube.com/watch?v=VG1FXiXP_lM
The only difference with the no-death route is that you can take a faster route through the barrel section right before the helicopter, without thinking about preparing for the fuel drop.

Helicopter - https://www.youtube.com/watch?v=oFmYHxtxXUw
The first rocket you shoot with the helicopter is almost instantaneous, while the next ones come with a long delay. This is fortunate since it makes it easier to set up a self-explosion while getting into the flying state. For safety, you can also time like it's shown in the video right before the kamikaze soldier explodes. If you for some reason miss to self-explode, the explosion from the kamikaze will still do the job.
At the end, the jump forward is guaranteed if you traveled in a straight line. It's not evident to take out all soldiers guarding the boss before the invincibility wears out. If you follow the steps in the video, it should be safe though.

Area 4

Foot2 - https://www.youtube.com/watch?v=LXrVBklJvQk
Roughly 8 seconds faster than in the tank (see no-death route). It's risky with all shooting blue soldiers though and there is also the potential for time losses to dispatch of enemies that are not present when in the tank.

Foot3 - https://www.youtube.com/watch?v=ZRk6L4WfDpo
The approach towards the helicopter from the right side of the water section is slightly faster than the left side. It has a very low probability of producing a fuel drop for the helicopter though, which is the reason it's not used in the no-death route.
It's important not to get into the helicopter "too fast". The risk if you're going too fast is that the last rail turret will fire a missile straight left instead of diagonally down when you're flying past it. You have to be fairly quick for it to fire to the left, so it's not always easy even if you want to try it out, but it's still good to keep this risk in mind.

Helicopter to end - https://www.youtube.com/watch?v=qaZSLsFo7R8
You'll save time by leaving the helicopter roughly in the range $70-$99 of small y (address $5B0). This allows leaving the flying state as early as possible, while getting a forward-jump, which will make the screen scroll during the death animation. The red diagonal stripe on the ground right after entering the helicopter is a good indication, just like is shown in the movie.
Also note that it's around half a second faster to kill the last boss with default grenades (the smaller explosion allows for a higher firing rate), which is the reason for not having collected a heart earlier in the level.
The last boss takes ten hits to kill. However, there is an anomaly/bug that makes some grenades not deal damage. The most common is that it either takes 11 grenades or 18/19 grenades. The exact reason for this is not known, but a few observations have been made from save states:

• The timing and the player's y-position appear to be important for when the boss takes 18/19 hits. It usually happens if you move without stopping after re-spawning and start throwing grenades around small y-position 114-118 (decimal).
• The 11-hit scenario appears to be more unpredictable. It also seems to be linked to the timing and the y-position, but different save states yield different results.
• Around the position shown in the video for starting to throw grenades has given good results for avoiding requiring additional grenades.
• The boss health is tracked among the drops addresses ($674 and onwards).