Note, all of the information on this page is from James Cameron's "Avatar".

The SA-2 Samson was developed by Aerospatiale to transport troops and cargo to sites not accessible by regular means of transport, and is generally a non-combat aircraft, though it can be armed with various kinds of machine gun and missile pod.

During its development on earth, it was designed so it could fly through any atmosphere, and stand up to any conditions it is put through, whether it be the freezing temperatures of antarctica, or different atmosphere density of Pandora. Because of this ability, the RDA on Pandora chose this as their main vehicle of choice.

(Apologies for the crappy comparison picture)
Also, I do take suggestions for future projects, so if you have any, fire away! Thanks!