What is the value of the initial horizontal velocity?

9.8 m/s/s

Explanation:

The horizontal velocity of a projectile is constant (a never changing in value), There is a vertical acceleration caused by gravity; its valueis 9.8 m/s/s, down, The vertical velocity of a projectile changes by 9.8 m/s each second, Thehorizontal motion of a projectile is independent of its vertical motion.

the horizontal component of the velocity, however, retains its initial value v0x=+115 m/s throughout the entire descent.

Explanation:

since the plane also travels at a constant horizontal velocity of +115 m/s, it remains directly above the falling package.