I don't know the figures but I'd imagine (guess) that somewhere in the region of 10% of Mispers are found by Air support? Most don't intend self harm but a few do....
...and some don't even know what they are doing, such as the misper we found walking towards the top of the Malvern Hills the other night in worsening weather, while everyone else was looking in the town.
IMHO; that night, the benefits of air support and mispers proven and case closed. Having said that....I wonder how long NPAS would have allowed us to look !