Really hard to tell for sure, but assuming it orients itself aerodynamically, exposing a 75x10mm surface area to the wind, with a drag coefficient of 1.0 (slightly less than a cube) and a mass of 180g, then omnicalc says it'd be moving at 225 km/h (62.5 m/s), giving a kinetic energy of 352 Joule.
If I had to guess - based on comparisons to energies cited for handgun bullets, less-lethal ammo, and punches - this could be fatal, but (given the relatively large size of the projectile) wouldn't be certain death.
There's also a chance of significantly more drag due to tumbling, which would likely put it into "most likely survivable but very, very painful" territory.
And assuming that hypothetical person wouldn't have survived, who would have been made liable for the person's death? The owner of the phone? Air Alaska? Boeing?
