The plane is a stock An-2.
This type of airplane is used for parachuting, paratrooper drops, flight training.
The plane is a gift from Mr. Church at the end of The Expendables 2, to replace the recently destroyed XP 2112 flying boat that the team previously used. It is festooned with a hammer-and-sickle design. It is imply that the plane will be once again appeared in the third film.