"The hull value of each friendly ship is increased according to its size class:
Rules Clarification Edit
Admiral Motti has no effect on huge sized ships.
FFG video (question answered at 29:31)
The effect of this Upgrade Card is permanent. If the flagship is destroyed, all ships of the fleet lose their additional hull point(s) immediatly.
Admiral Motti was the Chief of the Imperial Navy who held the rank of admiral aboard the Death Star in Episode IV: A new hope.