My third and final argument of the day is…. You guessed it. I refuse to let sleeping dogs lie. I’m here to fight about Drake and “his” Flamethrower again! (aka: the one he picked up!)
Bear with me here and try not to dismiss this too quickly. There
was an error and will address it, but the error was not the
reason he has the flamethrower.
Here is the ultimate argument.
-We know James Cameron is an obsessive detail freak & the hive scenes were among the first scenes filmed. As such, I refuse to believe that the first thing JC does on set is opt for a magically appearing heavy weapon. Hence, a logical explanation must exist. To find it, we don't need to look to far.
-3 marines were issued Flame units, so 3 units were on the battle field. All 3 marines with those units would be collected and hauled away by aliens. All 3 marines did
NOT utilize the sling at the time of combat.

Dietrich moments before scoop-age & previous shot of Ski carrying his weapon during sweep and explosion scene citing his continued preference to keep the sling in his hand. I have no pic for Apone, but he had just received the flamethrower from Frost to toast the chest-burster which kick started the action. I doubt Apone slung the weapon.
This means
theoretically, all 3 marines would
LIKELY have dropped their weapons where they stood, on the battle field and along the escape route. *(Yes I am aware Dietrich threw on the panic death grip on the trigger, but it couldn’t have gone far. Highly unlikely she held on to it all the way to her final cocoon).
So that would theoretically leave 3 units literally lying on the ground. -Drake is a badass right? Badasses know when ammo is gone and weapons are scarce to
NOT WALK PAST a perfectly useful weapon without picking it up. Any clear headed person would scoop up a weapon when they know useful weapons are in short supply. A badass one would excel at grabbing it quickly and efficiently.
Now that I’ve danced around the logistics of
why he could…BEHOLD PICTURES that I believe show he
DID!
-The first appearance of Drake with the flame thrower!!!!!! (pre- Ripley crashing through the wall, and right after the APC appears through the wall) Take special note of the Flame thrower ON TOP of his arm.

Dangling loosely over one shoulder, bouncing around, strung over the TOP of one’s arm and primary weapon, is
NOT how a marine carries a backup weapon into battle. BUT, you better believe that it
is how one stashes something they picked up quickly on the fly!!!



-Unfortunately, this next sequence really pisses me off.
Thisis the continuity error. This bit of poor editing is what, in my opinion clouds the entire issue. Between the above sequence, and the “running out of ammo” sequence is this dribble.

No flame unit. The lack of one here smack in the middle of the action makes it easy to say “continuity error” despite what the previous sequence set up.
-Right after that follows the sequence where he runs out of ammo. (with the flame thrower returned and in a more manageable position, which is conceivable that he wrangled that bouncing thing in a bit)

The first frame after he says “Shit” as he runs out of ammo is this, with the flame thrower un-slung and away from his body as he pulls the “escape cord” on the vest.

While not super telling, it does re-affirms that it was still over the top of one shoulder, not part of his gear or behind/under his rig or other equipment.
-My closing statement (finally! right?)
The idea of a “backup flamethrower” is great to high five your buddies over, but is an impractical and quite silly idea. I mean, look at that last picture. The pilot light was lit. If your saying he was just chilling with that the whole movie, it means he either lit the pilot one handed (from a "sling button"

), or it means it was just hanging there the whole time, bouncing around burning his ass, thighs and whatever else he brushed up against!
A much more practical explanation is it was still lit from the poor soul that went into combat with it. Just like it’s a much more practical explanation that James Cameron didn’t write a magically appearing flamethrower into the script. I'm sure he trusted us as viewers to figure out Drake scooped it up when the flame thrower first appears on Drake's person in this manner:

I rest my case*. High fives?!?!

*unless everyone just bashes me ruthlessly...then I may have a little cry and then rebuttle. But I am pretty sure I've said all that can be said.