Now for a bit of tricky explication which yours truly believes to be exactly correct in the classical limit of velocities much less than the vacuum light speed c = 2.99792458*10**5 km/s ≅ 3*10**5 km/s, weak gravitational fields (i.e., much weaker than near black holes) and on size scales much smaller than the observable universe.

Consider a free-fall frame Frame A. There will be an infinite continuum of nearby free-fall frames. Frame A will have acceleration with respect to each of them which will be different for each one in general. Consider free-fall frame Frame B. An observer in Frame B see the weightlessness in Frame A and can assign an inertial force that exactly cancels the gravitational field at Frame A minus the gravitational field at Frame B: the exact cancellation gives the weightlessness If Frame B had the same gravitational field as at Frame A, the assigned inertial force would be zero and Frame A would be unaccelerated relative to Frame B.

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