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=2AB4_HSCFt4
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=NVUXLTKxAHY
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/edit?o=U&video_id=KEyZiC3VQyA
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/edit?o=U&video_id=FCZWboNt-dQ
The approach towards the helicopter from the right side of the water section is slightly faster. 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.

Helicopter - https://www.youtube.com/edit?o=U&video_id=jieSWLPnyJs
Note how you need to move around one block to the left before leaving the helicopter to get the jump at the end (unknown reason). Be sure to not start moving diagonally right away though. If you move diagonally too early, the last jump will be shorter.
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.