Just finished watching TRON: Legacy for the third time and the same question persists: If these are digital creations then "air" and "atmosphere" would only be concepts like in the Matrix ("is that air you're breathing?"). How then do the white and orange Light Jets stall-out in the air at the end of the movie when Quorra takes them straight up vertically into what is known as a "Hammerhead Stall" which is a direct function of atmosphere? I assumed the activity of "flight" was more a digital representation of movement, that wind represented fast moving data, etc, but this suggests actual Bernoulli principles in operation (why real aircraft fly)...??? Is there actual air, actual atmosphere in The Grid??
In the grid, everything is function of the model Flynn programmed for it. Physic are well simulated, but some feat like the light cycle's 90 degree turns are just unrealistic.
As for Light jet, they are, or are running on, a flight simulation program. If the simulation is made to simulate a stall, It may be just because Flynn wanted to implement a maximum altitude to his jets program and the stall was an intuitive way to do it. An invisible ceiling would be another, although less elegant, way to force this limitation. It could be because he does not want to deal with overflow altitude values or another reason. However, the reason behind a stall in real life (air density) don't need to be implemented to properly simulate it.