This game has a connection smoothing code, as it's called. When a network lag occurs, the game won't stop but rather everyone keeps flying how they were at the moment you lost stability. The game on your front end is constantly trying to predict where planes are going at their present state (which is why a sharp maneuver will cause a plane to make an instant 90 degree turn on another computer sometimes).
So generally, if planes are flying one direction and suddenly begin to exist somewhere else, make random but consistent physically impossible maneuvers (as in it doesn't always happen when you're about to shoot them or something, but rather in level flight too), then it's probably a network problem.
If the game literally stops, it's trying to load something. This is usually trying to load a texture (usually a skin) from the hard drive, which is a slow process. These don't have to do with your network, but rather a local bottleneck or resource issue.
