This began with the adaptation of the He 70 and, in particular, the He 111, to be used as bombers. Heinkel also provided the Luftwaffe's only operational heavy bomber, the Heinkel He 177, although this was never deployed in significant numbers. The German Luftwaffe equipped both of these bombers with the Z-Gerät, Y-Gerät, and Knickebein, developed by Johannes Plendl, and thus they were among the first aircraft to feature advanced night navigation devices, common in all commercial airplanes today.