| 1 | HTX | Houston Tank Car Co. | 1/1952-10/1957; eliminated 4/1960 | | NAKINA |
| 2 | HTX | The Hewitt Transportation Co. (The Hewitt Soap Co., Inc.) | 7/1937-4/1938 | | NAKINA |
| 3 | HTX | The Hewitt Soap Co., Inc. | 7/1935 | | NAKINA |
| 4 | HTX | The Hewitt Soap Co., Inc. | Apr-38 | | NRHS |
| 5 | HTX | Houston Tank Car Co. | 1/52-10/57 | | NRHS |
| 6 | HTX | HEWETT SOAP CO., INC. (HEWITT TRANSPORTATION CO.) | | | PWRC |
| 7 | HTXC | HEAT TRANSFER LLC | | | SCAC4 |
| 8 | HTXG | HIRTE TRANSFER & STORAGE | | | SCAC4 |
| 9 | HTXI | HOPE TRANSPORT INC | | | SCAC4 |
| 10 | HTXL | HIALEAH TRANSPORT LLC | | | SCAC4 |
| 11 | HTXN | HEARNE TRANSPORTATION | | | SCAC4 |
| 12 | HTXO | HAT TRANSPORT LLC | | | SCAC4 |
| 13 | HTXT | HOLBORN TRANSPORT | | | SCAC4 |
| 14 | HTXU | JINGMEN HONGTU SPECIAL AIRCRAFT MANUFACTURING CO LTD | | PRC | BIC |
