Complex sentence: This statement was repeated for many years, and not publicly challenged because of the esteem of the Tuskegee Airmen, until 2004 when long-time Tuskegee admirer William Holton conducted research into wartime action reports.
Split into simpler sentences: This statement was repeated for many years, and not publicly challenged, perhaps because of the esteem of the Tuskegee Airmen. In 2004, long-time Tuskegee admirer William Holton conducted research into wartime action reports.