Exhibit 21.1 KNIGHT TRANSPORTATION, INC. SUBSIDIARIES 1. Knight Transportation Services, Inc., an Arizona corporation 2. Knight Management Services, Inc., an Arizona corporation 3. Knight Transportation South Central, L.P., a Nevada limited partnership 4. KTTE Holdings, Inc., a Nevada corporation 5. QKTE Holdings, Inc., a Nevada corporation 6. Quad K Leasing, Inc., an Arizona corporation