assuming no air friction, we know that the horizontal velocity does not change since there are no horizontal forces

this means we know the horizontal velocity is constant at 239 m/s throughout the flight, since the package has the same horizontal velocity as the plane

then horizontal distance = horizontal velocity x time

we find the time from

dist = 1/2 gt^2 where g=9.8 m/s^2 and dist = height = 4820 m

t = sqrt[2*4820 m/9.8m/s^2] = 31.36 s

so the horizontal distance = 239 m/s x 31.36 s = 7495.04 m