After a year of developmental testing of the B-29, Tibbets was assigned in March 1944 as director of operations of the 17th Bombardment Operational Training Wing (Very Heavy), a B-29 training unit based at Grand Island Army Air Field, Nebraska, and commanded by Armstrong. Its role was to transition pilots to the B-29. Crews were reluctant to embrace the troublesome B-29, and to overcome crew anxiety, Tibbets taught and certified two Women Airforce Service Pilots, Dora Dougherty and Dorothea (Didi) Moorman, to fly the B-29 as demonstration pilots, and the crews' attitude changed.