Back to Basics
Its all very simple really
Every take off and landing is a transition from one medium into another.
When you have transitioned into the air medium then ALL flight is with reference to the air you are in.
Granted there remains confusion when you are at the interface of the two mediums and there are cross over effects such as gusts.
As for momentum and inertia. Why has no one considered that the parcel of air we fly in is going around at the equator at about 1200 Kts. But it doesn't matter. The aircraft is aptly named. It flys relative to the air.