...or is the weightlessness experience just relative to a falling airframe?

You guessed it! They both just rise and fall at the same rate, so the "weightlessness experience" is just that, an experience no different than jumping off of a stool, except that it's longer because they jumped higher.

I'll add a link to Q&A here that address this in greater detail, and this may become a duplicate of that.

Is the gravity pull of the Earth negligible at 50 miles up...

No it's almost the same. Gravitational acceleration varies as

$$a = \frac{GM_{Earth}}{r^2}$$

Let's call 50 miles 80 km. Earth's equatorial radius is about 6378 km, so gravity at 80 km is

$$\left(\frac{6378}{6378+80}\right)^2 \approx 97.5\text{% of Earth.}$$

...or is the weightlessness experience just relative to a falling airframe?

You guessed it! They both just rise and fall at the same rate, so the "weightlessness experience" is just that, an experience no different than jumping off of a stool, except that it's longer because they jumped higher.

I'll add a link to Q&A here that address this in greater detail if/when I can find them. I'm pretty sure this has been explained in the context of the astronauts aboard the ISS; they're both "falling" or oribing the Earth, and up there gravity is about 85.5% that of the surface.