Originally Posted by
JimFromAustin
I have a question on how it is known the FMS was modified? Does the FMS report back the change in the flight plan via ACARS or something? Or is there just circumstantial evidence that it was changed? Sorry if this has already been asked, I scanned all the posts here and didn't see anything.
Seems to be based on aircraft path via radar track, there are ways to tell, but prefer not to detail those.
Bottom line, it appears to be speculation that the FMS inputs were altered.
They say it passed close to certain waypoints, but they would have been nailed with FMS input. This suggests heading inputs may have been made instead, or not.
Raw radar data may not accurately reflect path or altitude depending on type of radar and operator.