  A double--layer system in a strong perpendicular magnetic field is
considered. We assume a random potential in each layer to be smooth. We also
assume that there is no correlation between random potentials in different
layers. Under these conditions the equipotential lines from different layers,
corresponding to the same energy, may cross each other. We show that, if the
tunnel coupling between the layers exceeds some characteristic value (which is
much smaller than the width of the Landau level), then the probability for an
electron to switch equipotential (and, thus, the layer) at the intersection is
close to one. As a result, the structure of each delocalized state in a
double--layer system becomes completely different from that for an isolated
layer. The state is composed of alternating pieces of equipotentials from
different planes. These combined equipotentials form a percolation network. We
demonstrate that the regions, where equipotentials from different planes touch
each other, play the role of saddle points for such a network. The energy
separation between two delocalized states is of the order of the width of the
Landau level, and the critical exponent of the localization length is
$7/3$--the same as for an isolated layer.
