| 3001 | SEOY | SEA OIL CHARTERING (USA) INC | | | SCAC4 |
| 3002 | SEP | Serene Air (Private) Limited | IATA: ER, Founded in May 2016. AOC granted 18 March 2016. | PK | AVCODES |
| 3003 | SEPA | Southeastern Pennsylvania Transporation Authority (passenger commuter operation) | 1/1994-7/2005 | | NAKINA |
| 3004 | SEPA | Southeastern Pennsylvania Transporation Authority (passenger commuter operation) | 1/94-7/2000 | | NRHS |
| 3005 | SEPA | SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY (SEPTA) | | | PWRC |
| 3006 | SEPA | Southeastern Pennsylvania Transportation Authority (SEPTA) | | | RSRV |
| 3007 | SEPB | SPREE EXPEDITIONS INC | | | SCAC4 |
| 3008 | SEPC | SOUTHWEST ELECTRIC POWER CO. | | | PWRC |
| 3009 | SEPC | STEP2 COMPANY LLC, THE | | | SCAC4 |
| 3010 | SEPE | SHEPHERD ENTERPRISES LTD | | | SCAC4 |
| 3011 | SEPF | SERVICIOS PUBLICO FEDERAL CARGA GEN | | | SCAC4 |
| 3012 | SEPK | SHIP-IT EXPRESS II | | | SCAC4 |
| 3013 | SEPL | SEASONS TRANSPORTATION SERVICES | | | SCAC4 |
| 3014 | SEPN | SOUTHEASTEN SHIPPING LINE LTD | | | SCAC4 |
| 3015 | SEPO | SUMMIT ELECTRIC PRODUCTS | | | SCAC4 |
| 3016 | SEPQ | SPECIAL EVENT PRODUCTION INC | | | SCAC4 |
| 3017 | SEPR | South Eastern Provincial | | GB | TRAFFIC |
| 3018 | SEPS | SUREXPRE | | | SCAC4 |
| 3019 | SEPSA | Societá per l\'Esercizio di Pubblici Servizi SpA | | IT | VKM |
| 3020 | SEPTA | SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY | | | PWRC |
| 3021 | SEPTA | Southeast Pennsylvania Transportation Authority | | USA | TRAFFIC |
| 3022 | SEPX | Shell Eastern Petroleum Products | 7/1930 | | NAKINA |
| 3023 | SEPX | Shell Eastern Petroleum Products, Inc. | 7/1932-7/1935 | | NAKINA |
| 3024 | SEPX | Shell Union Oil Corp. | 7/1937-4/1938 | | NAKINA |
| 3025 | SEPX | Shell Oil Co., Inc. | 1/1941-1/1943 | | NAKINA |
| 3026 | SEPX | Southwestern Electric Power Co. | 1/1980-7/2005 | | NAKINA |
| 3027 | SEPX | Shell Eastern Petroleum Products (Shell Union Oil Corp.) | Apr-38 | | NRHS |
| 3028 | SEPX | Southwestern Electric Power Co. | 1/80-7/2000 | | NRHS |
| 3029 | SEPX | *SHELL OIL CO. | | | PWRC |
| 3030 | SEPX | +SOUTHWESTERN ELECTRIC POWER COMPANY | | | PWRC |
| 3031 | SEPX | Southwestern Electric Power | | | RSRV |
| 3032 | SEPX | SOUTHWESTERN ELECTRIC POWER COMPANY | | | SCAC4 |
| 3033 | SEQ | Sky Eyes Co. Ltd. | IATA: I6, Callsign: Sky eyes, | T | AVCODES |
| 3034 | SEQ | Sky Eyes Co. Ltd. | Callsign: Sky eyes, Designator I6 recalled by IATA | T | AVCODES |
| 3035 | SEQ | Sky Eyes | IATA: I6 | | ICAO1 |
| 3036 | SEQA | SEQUOIA AIR FREIGHT | | | SCAC4 |
| 3037 | SEQB | SAUNDERS EQUIPMENT LTD | | | SCAC4 |
| 3038 | SEQC | SELECT TRANSPORTATION SOLUTIONS INC | | | SCAC4 |
| 3039 | SEQD | SPECIALIZED EQUIPMENT RENTAL & DIST | | | SCAC4 |
| 3040 | SEQF | STEEL EQUIPMENT SPECIALISTS | | | SCAC4 |
| 3041 | SEQL | STEELE ENTERPRISE LLC | | | SCAC4 |
| 3042 | SEQP | SIERENS EQUIPMENT LTD | | | SCAC4 |
| 3043 | SEQQ | STRATTON EQUITY COOPERATIVE CO | | | SCAC4 |
| 3044 | SEQU | Simmonds Equipment | | | RSRV |
| 3045 | SEQV | SEA-MAR INC (CONTAINER DIVISION) | | | SCAC4 |
| 3046 | SEQX | Sequa Chemicals, Inc. | added 4/1997; 7/2000; eliminated 10/2002; 7/2005 (not listed) | | NAKINA |
| 3047 | SEQX | Sequa Chemicals, Inc. | added 4/97; 7/2000 | | NRHS |
| 3048 | SEQX | SEQUA CHEMICALS INCORPORATED | | | PWRC |
| 3049 | SEQX | Sequa Chemicals | | | RSRV |
| 3050 | SER | Aero California | IATA: JR, Callsign: Aerocalifornia, IATA Prefix: 078, | MEX | AVCODES |
| 3051 | SER | Sierra West Airlines | Callsign: Sierra, | USA | AVCODES |
| 3052 | SER | Aero California | IATA: JR | | ICAO1 |
| 3053 | SER | Proservis Ekspres Lojistik Hizmetleri San. Ve.Tic. A.Ş. | | TR | VKM |
| 3054 | SERA | Sierra R.R. Co. | 1/1975; added 1/1976; 1/1980; eliminated 1/1988; eliminated 10/1991; 1/1994-7/2005 | | NAKINA |
| 3055 | SERA | Sierra R.R. Co. | 1/75-1/80; eliminated 1/88; eliminated 10/91; 1/94-7/2000 | | NRHS |
| 3056 | SERA | SIERRA RAILROAD COMPANY | | | PWRC |
| 3057 | SERA | Sierra Railroad | | | RSRV |
| 3058 | SERA | SIERRA RAILROAD COMPANY | | | SCAC4 |
| 3059 | SERA | Sierra Railroad | | USA | TRAFFIC |
| 3060 | SERC | SPENCERVILLE & ELGIN RAILROAD CO. | | | PWRC |
| 3061 | SERC | SERCO INC | | | SCAC4 |
| 3062 | SERCO | Serco Group Plc | | GB | TRAFFIC |
| 3063 | SERCO | Serco Railtest | | UK | VKM |
| 3064 | SERD | SUN DIEGO CHARTER COMPANY | | | SCAC4 |
| 3065 | SERE | SERVICE EQUIPMENT&TRUCKING, INC | | | SCAC1 |
| 3066 | SERF | SERVICO DE FLETES Y MONTECARGAS | | | SCAC4 |
| 3067 | SERF | Servizi Ferroviari Srl | An FS Cargo subsidiary, operates nationwide in the sectors of planning, building and operation of railway sidings. | I | TRAFFIC |
| 3068 | SERG | SERG TRANSPORT, INC | | | SCAC4 |
| 3069 | SERH | SNELL, E R CONTRACTOR INC | | | SCAC4 |
| 3070 | SERJ | SERVICE TRANSPORT, INC | | | SCAC1 |
| 3071 | SERJ | SERVICE TRANSPORT INC | | | SCAC4 |
| 3072 | SERK | SMOKIN ELK RANCH LTD | | | SCAC4 |
| 3073 | SERL | SERTRAN LTD | | | SCAC4 |
| 3074 | SERN | SOLTERO | | | SCAC1 |
| 3075 | SERN | SOLTERO TRUCKING INC | | | SCAC4 |
| 3076 | SERP | SEA-TAC ROOFING SUPPLY INC | | | SCAC4 |
| 3077 | SERQ | SERTA MATTRESS | | | SCAC4 |
| 3078 | SERR | SIERRA INDUSTRIAL S A DE C V | | | SCAC4 |
| 3079 | SERSA | | | CH | TRAFFIC |
| 3080 | SERSA | Sersa Group Management AG | | CH | VKM |
| 3081 | SERSD | Sersa GmbH | | DE | VKM |
| 3082 | SERT | SOUTHWEST CONTAINER TRANSPORT | | | SCAC4 |
| 3083 | SERU | SU-EUROPE RIVER&RAILWAY CONTAINERS TRADING AND LEASING CO LIMITED | | PRC | BIC |
| 3084 | SERU | SERMAR LINE SRL | | | SCAC4 |
| 3085 | SERVICES | CHICAG | | | SCAC4 |
| 3086 | SERX | Service Tank Car Co. | 7/1930-4/1938 | | NAKINA |
| 3087 | SERX | Shippers' Car Line Corp. (Service Tank Car Co.) | 1/1941-7/1954 | | NAKINA |
| 3088 | SERX | Shippers' Car Line Corp. | eliminated 7/1956 | | NAKINA |
| 3089 | SERX | Shippers' Car Line Division of ACF Industries, Inc. | added 7/1956; 10/1957-1/1975; eliminated 1/1976 | | NAKINA |
| 3090 | SERX | Shippers' Car Line Division, ACF Industries, Inc. | added 1/1976; 1/1980; eliminated 4/1988 | | NAKINA |
| 3091 | SERX | ACF Industries, Inc. | added 4/1988; 1/1994-7/2000; eliminated 4/2005 | | NAKINA |
| 3092 | SERX | American Railcar Leasing, Inc. | added 4/2005; 7/2005 | | NAKINA |
| 3093 | SERX | Service Tank Car Co. | Apr-38 | | NRHS |
| 3094 | SERX | Shippers' Car Line Corp. (Service Tank Car Co.) | Jan-52 | | NRHS |
| 3095 | SERX | Shippers' Car Line Corp. | eliminated 7/56 | | NRHS |
| 3096 | SERX | Shippers' Car Line Division of ACF Industries, Inc. | added 7/56; 10/57-1/80; eliminated 4/88 | | NRHS |
| 3097 | SERX | ACF Industries, Inc. | added 4/88; 1/94-7/2000 | | NRHS |
| 3098 | SERX | *SOUTHERN ELECTRIC RAILROAD | | | PWRC |
| 3099 | SERX | +AMERICAN RAILCAR LEASING, INC. [ACF INDUSTRIES, INC.; SHIPPERS' CAR LINE CORP. (UNION CARBIDE - LESSEE)] | | | PWRC |
| 3100 | SERX | ACF Industries Shippers Car Line Division | | | RSRV |
