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. How this works is described in flying glitch.

Area by area description

The videos for each area are divided into sections, where there is a change of vehicle or where it would have been possible to enter a vehicle.

Area 1

1 - Foot - https://www.youtube.com/watch?v=YcY76B0C-TY

2 - Tank - https://www.youtube.com/watch?v=w2eMvRqP_44

• All the upgrades (F, S and L) are absolute requirements for the route to work. The first part is plagued by random grenade thrower spawns. They should only occasionally be able to hit you, but they're still an annoyance.
• If there are three or more soldiers on screen, the green tank on the bridge will not spawn (because of the sprite limit). If that happens, you can take it out with a diagonal shell instead. A problem arises if the tank spawns before you're in position for the diagonal shot. It's therefore often best to try to rid the section before the tank of blue soldiers, if possible.
• On the last stretch, blue soldiers frequently spawn on the left side. If they don't run into the tank, they will home in on you and catch up to you once you leave the tank. They can easily be taken care of by laying a carpet of grenade shells on the left side though.
  

3 - Foot - https://www.youtube.com/watch?v=6WeFUcxeAzI
There are four or five enemies you need to care about here. The optional one (not shown in this video) is a blue spawn that will come at you when leaving the tank. This soldier has to be shot down. Sometimes he comes at a bad angle and you need to adjust (for a small time loss) in order not to run into him. The other four can easily be taken care of with grenades as shown here. The first one is a machine gunner that will also home in on you. The next two are self-exploding guys and the last is the rapid machine gunner right before the helicopter. Maybe 5-10% of the time, the mine will kill you if you walk in a straight line. If you want to reduce that risk (at the cost of a few frames) you can slightly tilt to the left when you're walking alongside it.

4 - Helicopter/flying glitch - https://www.youtube.com/watch?v=-WWq-4Eunlw
The flying glitch is described in the flying glitch section. The end of the area is reached when the character's y-position reaches 45. The most optimal is therefore to leave the helicopter when the y-position is between 0 and around 44, which will result in a teleportation jump to the end. A suitable visual indication for this is when the front of the helicopter is a little before the first island on the left side.

Area 2

1 - Foot - https://www.youtube.com/watch?v=69ZZGMEpQyw
This part of the game is tricky even with all the upgrades because of many possibilities for random spawns. Starting without upgrades (because of not collecting the heart in area 1 and flying over some of the important items) makes it even harder. The key areas where survival will have to take priority over speed is from the open area where the SS is found (this place can be crawling with shooting blue soldiers) until the first water section. But random spawns can pop out of no where in several other places as well and cause trouble.

• Any blue soldiers that come close to the right side around the SS item will likely be a considerable threat. Many of the movement patterns of these soldiers will bring them in your way (including firing your way), so it's recommended to stop and take them out, even if it means a time loss.
• If the big tank doesn't shoot a grenade as you approach (RNG), you can clear the bridge area ~40 frames faster, https://www.youtube.com/watch?v=NWnPupDT-gY.
• It's possible to manipulate the tank into firing diagonally into the water instead of on the bridge. You need to pause briefly between the bridges. Overall, this approach would be a second faster or so since you don't have to wait for the explosion of the shell on the bridge. The pause has to be accurate down to the minimum time window of four frames and unfortunately appears to depend on player position and likely global timing (when the tank decides to shoot), which means this time save comes at comparatively high added risk.
• There are three guaranteed spawns at the first beach. The pink soldier (harmless), a self-exploding guy (taken care of by the grenade) and another blue soldier. The latter will surface and hit you if you don't take it out with the gun as soon as it appears on screen. The problem in this area is instead the random blue soldiers. They both like to run into you and shoot you. There is no real guideline for how to deal with them. The firing and movement patterns in this video have been developed to take out many of the possible spawns, but are far from guaranteed to work in all cases.
• There is a knife on the left side of the first beach (see Level Maps). It would make the rest of the section easier, but is a bit out of the way and would cost 3 seconds. It also increases the chances of getting more random spawns in the water, which adds risk.
• It's preferable to keep the pink soldier and the accompanying blue soldiers at the end of the first water area alive. They will help prevent the spawning of blue machine gun soldiers on the beach right after.
• The airstrike target plate after the first water section is problematic. With the route shown in this guide, the airstrike will often come from a position so far off that it will not reach the target before it goes off-screen. The airstrike will then be "confused" and find a different target to follow. In practice, this often creates a risk since the airstrike moves quite fast and the blast from when it finally explodes will often be close to you. More information about the airstrikes can be found at airstrikes. The best way to deal with this is to pause before the target plate is scrolled off-screen to ensure that the airstrike connects with the target plate.

2 - Foot - https://www.youtube.com/watch?v=r_GXO64KVPI

• Entering one of the tanks around the stone faces will end up costing ~15 seconds compared to getting through the section on foot. One reason is that the tank will have to take a detour around the white structure because of the marshes.
• There is a knife in the left passage of the white fort. This is around one second slower than what's shown in the video, but also reduces the risk by quite a bit.
• The section right behind the white gate is risky. The big man's movements are manipulated to avoid collision. This is done by not moving left too early and is 100% consistent. This adds a lot of restriction on your movements though, which is risky in a section like this with so many possibilities for random spawns. Spending the second to collect the knife reduces some of the risk, but not all of it.
• There are many grenades that are tossed that appear to be a bit random in this video. They are based on anticipating possible enemy spawns that can cause trouble. These mitigations are however no where near covering all possible enemy patterns.

3 - Foot - https://www.youtube.com/watch?v=rtou8NSwJJg
The biggest risk in this section is to get bad spawns at the beginning of the fortress.

3 and 4 - Tank - https://www.youtube.com/watch?v=2EIX8pgjl-I

• With one exception, these sections are almost a formality in the tank. The tricky part is around the gate. There is a missile target plate that is very inconveniently placed and that creates a non-negligible risk of taking an unavoidable hit (a risk that is hardly present when on foot).
• Using the tank as shown here is around 13 seconds slower than on foot.

4 - Foot - https://www.youtube.com/watch?v=a7LjQpbMqNk

• There are quite a few half-diagonal shots in this section. All of them can be replaced by regular shots or grenades, but for minor time losses. For some of them, you might as well fire off a few shots and hope that at least one of them is a half-diagonal shot.
• Note that you are likely to need the weapon refill from the gate. It's not too uncommon that the gate doesn't spawn due to the sprite limit so you can't get to the drops. In that case, you take out the maching gun hide-out on the right side a little after the gate. That route is one second slower though.
• The second helicopter on the lnog bridge can be a bit problematic. There is some variation to when it fires its gun and some patterns will tag you when trying to pass by on the right side. This can be avoided by a strategic pause or by avoiding to run too far on the right side (too far to the left obviously won't work either, so somewhat precise positioning is needed).
• Taking out all the tanks in one go after the two big men is consistent, but requires a well-timed grenade toss. There is also a risk of the last tank not spawning in time if there are two or more blue soldiers on screen (sprite limit). If this is the case, it's often better to briefly pause to ensure at least one of the soldiers disappears off-screen. Even better is of course to eliminate the blue soldier(s), assuming they are within range.
• At 2:26, you can also go straight. If there are no enemies (rare), it's ~half a second faster to go straight. If there are enemies, straight and right are time-wise the same, but it's usually a little more risky to go straight. If you go right, you won't get the heart here, but it can be collected without time loss right before the end of the stage instead. It boils down to preference which path to choose.
• At 2:37, you have again two paths to choose from. Left is shown here, but it's time-wise the same (or at least very close) as going to the right. There doesn't appear to be a big difference in risk either (but right has been significantly less investigated).

5 - Foot - https://www.youtube.com/watch?v=rIs1Dm-v3z4

• If you're too fast past the first tank in the pink structure, it might fire a second missile horizontally instead of diagonally down. This is easily prevented by introducing a quick pause before it has shot the second shell.
  
• There is a faster (and riskier) path through the first part of the pink fortress: https://www.youtube.com/watch?v=vEP0xvtDRlo.

Area 3

Foot1 - https://www.youtube.com/watch?v=-eGQLme7jFM
Easy. The only part where you have to be a bit careful is to not miss the shot at the grenade thrower.

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.
There is a passage in the green pipe section, where you can get stuck (= you can neither move left nor up) when trying to squeeze between a green pipe and a pyramide structure. The rules for getting stuck are complicated and different ranges of x- and y-position combinations (including sub-pixels) will see you stuck. It's therefore difficult to see how this could be mitigated in real-time. Fortunately, getting stuck shouldn't happen more than 20% of the time or so (ballpark guess). If you do get stuck, it will always be possible to move diagonally down-left or up-right to get unstuck and allow you to pass through.

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 from that early on will happen if you entered the flying state with a small y-position (tracked in $5B0) of around $80-$B0. The first possibility of getting into that range is slightly before the kamikaze soldier straight-ahead, like shown in the video.
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.
The only input to the calculation of the position of the stairs to area 4 is the value of the global counter in $55 at the moment of dealing the last damage to the boss (the boss's RAM-addresses are transferred to the stairs at this point). The sub-routine performing this calculation starts at instruction $AC2C. There are 8 possible positions. The position changes every 16 frames (from left to right) meaning it cycles through every 128 frames (8*16). If you take a time stamp somewhere during the flying part, it's not unrealistic to at least get an idea of where to expect the stairs to be located. This obviously assumes that you always start with a fixed delay from the start screen and a time-wise consistent boss fight.

Area 4

Foot1 - https://www.youtube.com/watch?v=rQg5hd8xGAc
The area before arriving at the pools is fairly consistent. There is always a possibility of random blue spawns that can interfere with the route though. In the pool area, make sure you toss a grenade just as you're at the corner of the first pool. Then keep holding down A (and B of course). If you walk in a straight line, you will then also toss a grenade when you're at the corner of the second pool. This will guarantee that you take out the most important enemies (including the last self-exploding guy). There can still be random enemy spawns that can kill you. If you practice this area enough, you'll start recognizing which of the random enemies that will kill you (the rng is again rather predictable, although there are many different patterns to look for). Overall, while this section looks tough, it's fairly consistent as long as you follow the path shown here and practice how to recognize dangerous spawn patterns.

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 - 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).