Another irritant was a professional one for African-American officers. They observed a steady flow of white officers through the command positions of the group and squadrons; these officers stayed just long enough to be "promotable" before transferring out at their new rank. This seemed to take about four months. In an extreme example, 22-year-old Robert Mattern was promoted to captain, transferred into squadron command in the 477th days later, and left a month later as a major. He was replaced by another Caucasian officer. Meanwhile, no Tuskegee Airmen held command.