[NBJack]

Yes. It would cascade into:

Changes in how ATCs operate

Changes in how pilots operate

Changes in how airplanes receive these instructions (including the flight software itself, safety systems, etc.)

Changes in how airplanes are tested

Changes in how pilots are trained

Etc. In this case, the refactoring requires changes to hardware, software, training, manufacturing, and humans.

[deadfish]

Pretty sure that is still not the meaning of refactoring. As I understand it refactoring should mean no changes to the external interface but changes to how it is implemented internally.

[LelouBil]

You could see it as the whole international flight system being refactored, consumers will still use planes like before

[NBJack]

We can pontificate on how to define the scope of a system here. I will only state that, from the perspective of a consumer, you could consider this a Service on which the interface of find flight, book flight, etc. would appear to be the same while the connections internal to each of the above modules would have to account for the change.

Functionally, I suppose it's the equivalent of upgrading an ID field that was originally declared as an unsigned 32 bit integer to a wider 64 bit representation. We may not be changing anything fundametal in the functionality, but every boundary interface, protocol, and storage mechanism must now suffer through a potentially painful modification.

[ftxbro]

does refactoring mean literally any non-local change even just like changing a variable name, or does it usually mean some kind of structural or architectural non-local change