| 1 | SEP | Serene Air (Private) Limited | IATA: ER, Founded in May 2016. AOC granted 18 March 2016. | PK | AVCODES |
| 2 | SEPA | Southeastern Pennsylvania Transporation Authority (passenger commuter operation) | 1/1994-7/2005 | | NAKINA |
| 3 | SEPA | Southeastern Pennsylvania Transporation Authority (passenger commuter operation) | 1/94-7/2000 | | NRHS |
| 4 | SEPA | SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY (SEPTA) | | | PWRC |
| 5 | SEPA | Southeastern Pennsylvania Transportation Authority (SEPTA) | | | RSRV |
| 6 | SEPB | SPREE EXPEDITIONS INC | | | SCAC4 |
| 7 | SEPC | SOUTHWEST ELECTRIC POWER CO. | | | PWRC |
| 8 | SEPC | STEP2 COMPANY LLC, THE | | | SCAC4 |
| 9 | SEPE | SHEPHERD ENTERPRISES LTD | | | SCAC4 |
| 10 | SEPF | SERVICIOS PUBLICO FEDERAL CARGA GEN | | | SCAC4 |
| 11 | SEPK | SHIP-IT EXPRESS II | | | SCAC4 |
| 12 | SEPL | SEASONS TRANSPORTATION SERVICES | | | SCAC4 |
| 13 | SEPN | SOUTHEASTEN SHIPPING LINE LTD | | | SCAC4 |
| 14 | SEPO | SUMMIT ELECTRIC PRODUCTS | | | SCAC4 |
| 15 | SEPQ | SPECIAL EVENT PRODUCTION INC | | | SCAC4 |
| 16 | SEPR | South Eastern Provincial | | GB | TRAFFIC |
| 17 | SEPS | SUREXPRE | | | SCAC4 |
| 18 | SEPSA | Societá per l\'Esercizio di Pubblici Servizi SpA | | IT | VKM |
| 19 | SEPTA | SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY | | | PWRC |
| 20 | SEPTA | Southeast Pennsylvania Transportation Authority | | USA | TRAFFIC |
| 21 | SEPX | Shell Eastern Petroleum Products | 7/1930 | | NAKINA |
| 22 | SEPX | Shell Eastern Petroleum Products, Inc. | 7/1932-7/1935 | | NAKINA |
| 23 | SEPX | Shell Union Oil Corp. | 7/1937-4/1938 | | NAKINA |
| 24 | SEPX | Shell Oil Co., Inc. | 1/1941-1/1943 | | NAKINA |
| 25 | SEPX | Southwestern Electric Power Co. | 1/1980-7/2005 | | NAKINA |
| 26 | SEPX | Shell Eastern Petroleum Products (Shell Union Oil Corp.) | Apr-38 | | NRHS |
| 27 | SEPX | Southwestern Electric Power Co. | 1/80-7/2000 | | NRHS |
| 28 | SEPX | *SHELL OIL CO. | | | PWRC |
| 29 | SEPX | +SOUTHWESTERN ELECTRIC POWER COMPANY | | | PWRC |
| 30 | SEPX | Southwestern Electric Power | | | RSRV |
| 31 | SEPX | SOUTHWESTERN ELECTRIC POWER COMPANY | | | SCAC4 |