After a series of numbered but unbuilt designs, Władyslaw Zalewski spent his spare time evolving the simplest and cheapest single seat aircraft on which to learn to fly.

Part-time construction began slowly in 1926 in his workshop at Milanówek, though in the following spring Zalewski made a determined attempt to have it ready for the First National Lightplane Contest, scheduled for that autumn.

The horizontal tail was mounted at mid-fuselage and had an unusual plan which led to the "Cockerel" name: the wire-braced tailplane's leading edges tapered strongly from the root with concave curvature out to forward projecting spurs.

The wheels, with rubber cord shock absorbers, were on a single axle attached to two skids mounted on the lower fuselage sides with a pair of cross-bracing struts between them.

It took part in the Second National Lightplane Contest in 1928 but engine problems restricted it to ninth place, though it did win a Ministry of Transport prize for the shortest landing distance (70 m (230 ft)).