The force of primary importance acting on a projectile is gravity. This is not to say that other forces do not exist, just that their effect is minimal in comparison. A tossed helium-filled balloon is not normally considered a projectile as the drag and buoyant forces are as significant as the weight. Helium-filled balloons can't be thrown long distances and don't normally fall. In contrast, a crashing airplane would be considered a projectile even though the drag and buoyant forces are much greater in absolute terms.
Gravity acting on a massive airplane is what really determines what happens.
Normal amounts of drag and buoyancy aren't large enough to save the passengers on a doomed flight from an unfortunate end. An essential characteristic of a projectile is that it future has already been preordained. No amount of leaning to one side will make a foul ball turn fair. Of course, the pilot of a disabled airplane may regain control before crashing and avert disaster, but then the airplane wouldn't be a projectile anymore. An object ceases to be a projectile once any real effect is made to change its trajectory.