From higher goddamn ground. Stop. Flying. Low. The only reason they were shot down is because stupid natives could get close to them, since they were flying too low. I mean, hell, that thing is capable of doing transorbital flights, with multiple reentries. Bring it somewhere higher willya?
The problem is, you go higher and there are now a bunch of floating mountains between you and your target.
Also, GPS doesn't work, so you don't actually know where the target is in the first place. That mountain range was huge, there was no way in hell they were ever going to hit the tree just firing blindly at it.
And yes; they were a mercenary 'guard' operation, not a military force. They didn't have any heavy munitions or bombers in the first place.
They had demolition charges. Makes good enough explosives.
They had ATTACK HELICOPTERS too. Really?
Sides, I failed to spot a single flying rock above the tree.
Have you
seen the Pandoran wildlife? Attack helicopters count as 'Light Munitions'.
And actually, demolition charges make shitty bombs. They make
great demolition charges though. Odd that.
A quick check also shows that the tree was covered in giant stone arch things, and that there were plenty of floating mountains above the shuttle as it was flying around. So it's safe to say there probably wasn't much in the way of 'clear line of sight' for a high altitude bomb run. And even if there was, there was no way to target the bomb run anyway, cuz the mountains EM field fucks up targeting systems.
It's a heavily armed military base on a planet filled with hostile natives.
Also, American.
Can you say bomb happy?
It's a lightly armed civilian base with a small mercenary force for self defense. Plenty of guns, not much in the way of bombs.
Everything the Sky People military had was supposed to be for guarding the base and mining operations against Pandoran wildlife. Bombs tend not to be defensive weapons. Bombs are also usually used against fixed and\or entrenched targets, something you're not going to find much of when your main enemy is wildlife and tribal natives fighting a geurilla war.
And, as i said before, even if they did have bombs, they had no way to deliver them to the target.
--EDIT--
Also i feel i should add;
the Humans won. They beat the Na'vi. They won. They won right up until the planet itself decided to kick their ass.
At that point it didn't matter if they were a fully fledged military force or not, when
every living thing on the entire planet resolves to kill you, you are
dead.
And technically even then, they were still winning. The only reason the shuttle went down was because Jake had nicked some grenades from somewhere; if he didn't have those, then even with the entire planet against them they still would have blown up that damn tree.