Imbracable Crunk has answered the original question clearly, putting basic Newtonian dynamics in qualitative terms. Other forces might come into play, but the question is which is the most influential, and this answer shows it.
Now for the intriguing question. How do flying wings such as the B2 , which have no find or rudder, coordinate turns? If you think the B2 does it with sophisticated electronics, then answer the same question for a flexwing microlight.
Concerning the contribution from SomeGuyOnTheDeck, I agree with him that a basic understanding of physics is helpful, but a basic understanding of aerodynamics is even more helpful!
Some airplanes can maintain knife-edge flight. All that is necessary is that the lift produced by the body flying sideways, coupled with the vertical component of engine thrust, equals or exceeds the weight of the aircraft, and that the rudder has enough aerodynamic authority to hold the nose up. What no airplane without thrust-vectoring can do is maintain knife-edge flight without yaw.
One should also be a little careful about such statements as
Originally Posted by SomeGuyOnTheDeck
..... qualified airline pilots apparently not understanding that one can recover from a stall by pushing forward on the control column/sidestick...
It is not as simple as that. There are some airplanes for which, when they stall, no amount of nose-down elevator command will recover it. These airplanes are mostly fitted with a stick pusher, to apply forcibly a nose-down pitching moment before the airplane gets into the unrecoverable part of the stall.
Saying this, of course, brings us back to what "stall" is. It is mostly a range of aerodynamic phenomena, and what exactly happens can be different according to the range of airspeed chosen. Some people think, for example, that the point of stall can be defined as the point of maximum coefficient of lift, but this is not necessarily so according to certification criteria, which allow that sufficient buffeting can define the point of "stall", even though maximum lift may not yet have been attained. And so on.
PBL