The Boeing NB (or Model 21) was a primary training aircraft developed for the United States Navy in 1924. It was a two-bay equal-span biplane of conventional configuration with interchangeable wheeled and float undercarriage. The pilot and instructor sat in tandem open cockpits. The NBs were produced in two batches; the first (NB-1) were powered by radial engines and the second by war-surplus Vee-8s still in the Navy's inventory.
Made by Boeing.