As a private pilot who has done a bit of aerobatics, I disagree. It still is a positive AoA. Using a negative would be in conflict with what you would mean when

As a private pilot who has done a bit of aerobatics, I disagree. It still is a positive AoA. Using a negative would be in conflict with what you would mean when you mean.. well, a negative AoA, for example when people ask questions such as this one: https://aviation.stackexchange.com/questions/51477/do-negative-angles-of-attack-create-lift https://aviation.stackexchange.com/questions/51477/do-negati... I would use AoA in relation to the direction of flight, not the up or down orientation of the airplane. Even upside down I still fly quite normally (in straight & level upside-down flight), and the lift created is positive: Up/down in relation to the earth don't change, so the direction of lift does not change. In this context it would be a bit confusing to use negative numbers as you suggest, IMO. However, since you can set your relative coordinate system and context however you like this is a topic we could discuss this ad infinitum without convincing one another if we insist on our respective PoVs. When faced with the linked question you would have some more explaining to do though, because there are negative AoA and no upside-down flight (now imagine adding that to the question to make it even more confusing...) :)