How accurate are flight paths filed by airlines before the flight? Specifically:
- Do they usually stick to the flight path that they file?
- If/when they deviate from the flight path in-flight, is it usually small, inconsequential deviations (in terms of distance from the original path), or a very large deviation or entirely different route?
I am specifically asking regarding the portion of the flight path for when the plane is cruising, not the flight path for takeoff or approach.
The reason for my question is that I am trying to make a program to make different sun-position-based calculations for a flight, i.e. when sunrise and sunset will be on the flight, so I am wondering if I can get the pre-filed flight path and use that to predict when things will happen with relative accuracy (such as sunrise will be around 4 hours into the flight), or if the pre-filed flight path can be entirely different than the route that the plane actually takes.