Do we want to accept this?
Are there better alternatives?
Personally, I think that flight-dynamics is a subset of aircraft physics, not a synonym, so I don't think the tags should be merged.
I do not think that they should be merged.
Consider a question about the the distribution of fuel in a wing, and its effect on the structure of the wing (stress, strain, etc.) at rest.
The tag description of aircraft physics is:
Physics as they apply to aircraft, including aircraft motion, forces affecting an aircraft, and stability and control.
That of flight dynamics is:
...the study of the physics driving the performance, stability, and control of aircraft. It is concerned with how forces acting on the aircraft influence its speed, altitude and attitude with respect to time.
So as stated here, flight dynamics is a sub-set of aircraft physics. As is aircraft-structures, hydraulic-system, electric-system, air-conditioning, aerodynamics - in fact most other tags. Taken literally, [aircraft-physics] seems way too broad.
From the definition of the tag, it looks as if the original intent of the tag was indeed to describe flight-dynamics since these are explicitly stated. It would make sense to me if [aircraft-physics] was merged with [flight-dynamics], and if a question on aircraft structures would be tagged [aircraft-structures]