Not much to work with but...
This seems kinda cool. The idea is unoriginal, but interesting nonetheless.
I like your graphics. Your sprite drawings are pretty good, and the way you made the backgrounds and objects is somewhat attractive.
Some stuff to work on:
You'll probably hear this a lot, you need SOUND! Even in a demo like this you need to put some sounds. Half of the whole feel of a game like this is the sounds. The sounds of the planes and the flak exploding in the air right next to you. The sounds of the AA guns, rifles, turrets, etc. going off all around you. The general warzone noises. It screws everything up if you don't have that.
Your interface is not good. Aim, ammo, and constant interactivity are completely thrown out the window when you make it just a button interface. Give us the gun, a cross-hair, a reload button, and preferably a hide button (a la Time Crisis), and let us do all the work. Thats the fun part of it.
Too short. If this is a preview of something you might make, please make it longer, or at least put it in segments/episodes and make several of them. Also the title is a bit misleading. "Airbourne" suggests a jet-fighter type of thing, while this was merely a paratrooper entrance. Just a small thingy
Your idea is very nice. With a shooter theme like this, you've got to combine a WWII warzone with Time Crisis or Virtua Cop action and interfeace. Do it nicely, and it'll be a hit. Keep going!