While, that is always a possibility (especially when the chicks may lunge for food, or when they get to "pushing and shoving" each other, or they happen to be too close to the edge when a big gust of wind blows through) luckily at this nest site that hasn't happened. And, if it does, hopefully, the chick would be feathered enough to have a soft landing.
Peregrines generally take their first flights at about 40 days old. Counting forward from the first hatch (April 19) that takes us to later this holiday weekend. It is generally the males that fledge first as they are smaller than the females. We don't have the exact make up of this clutch but do suspect perhaps 3 females and 1 male. Hopefully, all will wait until after the Memorial Day holiday to begin to fly. We'll post more information on fledging later this week.