A defense barrier for protecting a target from critical damage from the impact
of a predetermined group of aircraft comprises: a plurality of towers spaced from
the target, each tower being spaced from a neighboring tower by a distance less
than the wingspan of an aircraft in the predetermined group of aircraft having
the smallest wingspan in the group; each tower being spaced from the target at
least a distance d given by the formula: d=h/tan(theta) where h is the height of
the tower and theta is the smallest vertical approach angle of any aircraft from
the predetermined group of aircraft sufficient to inflict critical damage to the target.
