Force is equal to the rate of change of the momentum of the particle:
F = dp/dt
The momentum of a particle in relativistic mechanics is calculated by the formula:
p = m v/√(1 - v2/c2)
If you substitute this in the above equation (keeping in mind that the velocity vector has a constant direction during a linear motion, so that we can eliminate the vectors), and differentiate, you get:
F = m/(1 - v2/c2)3/2 dv/dt
Now, dv/dt is the acceleration wrt the inertial reference frame, and, as is seen from my previous post, it is dependant on velocity by the formula:
a = dv/dt = g (1 - v2/c2)3/2
Substituting this in the equation for the force, you see that the velocity factors cancel out and all that's left is:
F = m g
That means that the UA exerts a constant force on the Earth. It also means that you phail. Now die!