| 2401 | SDNG | SUMPTER, DON TRUCKING INC | | | SCAC4 |
| 2402 | SDNH | SHANGHAI DINGHENG SHIPPING CO LTD | | | SCAC4 |
| 2403 | SDNI | SHERIDAN TRUCKING INC | | | SCAC4 |
| 2404 | SDNJ | SAND STONE SERVICES LLC | | | SCAC4 |
| 2405 | SDNK | SANDMAN TRUCKING | | | SCAC4 |
| 2406 | SDNM | ST DENIS MANUFACTURING | | | SCAC4 |
| 2407 | SDNN | S & D TRANSPORT INC | | | SCAC4 |
| 2408 | SDNO | STANDARD DISTRIBUTION CO | | | SCAC4 |
| 2409 | SDNQ | STEWART, DON A INC | | | SCAC4 |
| 2410 | SDNR | SAN DIEGO NORTHERN RAILWAY | | | PWRC |
| 2411 | SDNR | San Diego Northern Railway | | | RSRV |
| 2412 | SDNR | SIDNEY TRANSPORT LTD | | | SCAC4 |
| 2413 | SDNT | STD TRANSPORT LTD | | | SCAC4 |
| 2414 | SDNU | SEDNA CONTAINERS B.V. | | NL | BIC |
| 2415 | SDNW | SNUG DUE SOCIETA NAVALI UNITE GENOV | | | SCAC4 |
| 2416 | SDNX | North County Transit District d/b/a San Diego Northern Ry. | 7/2005 (not listed) | | NAKINA |
| 2417 | SDNX | NORTH COUNTY TRANSIT DISTRICT d/b/a SAN DIEGO NORTHERN RAILWAY | | | PWRC |
| 2418 | SDNX | SAN DIEGO NORTHERN RAILWAY | | | SCAC4 |
| 2419 | SDNX | San Diego Northern Railway | | USA | TRAFFIC |
| 2420 | SDO | Aerolineas Santo Domingo, S.A. | IATA: EX, Callsign: Aero Domingo, IATA Prefix: 309, Founded in 1996. Merged with Servicios Aereos Profesionales, Inc. (SAP Air) during 2005. | DOM | AVCODES |
| 2421 | SDO | Air Santo Domingo | IATA: EX | | ICAO1 |
| 2422 | SDOB | SAN DIEGO COPIERS & OFFICE PRODUCTS | | | SCAC4 |
| 2423 | SDOE | SHIELDS RODEO | | | SCAC4 |
| 2424 | SDOG | STEINER, DOUG TRUCKING | | | SCAC4 |
| 2425 | SDOH | SPECIAL DISPATCH OF HOUSTON INC | | | SCAC4 |
| 2426 | SDOL | SNYDER DISCOUNT OIL | | | SCAC4 |
| 2427 | SDOMM | Santo Domingo Metro | | DOM | TRAFFIC |
| 2428 | SDON | STOCKLEY, DON TRUCKING LLC | | | SCAC4 |
| 2429 | SDOP | SOPROMAT LTD | | | SCAC4 |
| 2430 | SDOR | SUDDATH RELOCATION SYSTEMS OF ORLAN | | | SCAC4 |
| 2431 | SDOS | SDS LOGISTICS INC | | | SCAC4 |
| 2432 | SDOT | SHADOW TRUCKING, INC | | | SCAC1 |
| 2433 | SDOT | SHADOW TRUCKING INC | | | SCAC4 |
| 2434 | SDOU | SPINNAKER EQUIPMENT SERVICES INC. | | USA | BIC |
| 2435 | SDOV | SEATRADERS OVERSEAS INC PANAMA | | | SCAC4 |
| 2436 | SDOY | SHELDON OIL COMPANY | | | SCAC4 |
| 2437 | SDP | Aero Sudpacifico, S.A. | Callsign: Sudpacifico, | MEX | AVCODES |
| 2438 | SDP | Aero Sudpacifico | | | ICAO1 |
| 2439 | SDPD | SISTEMAS DE TRANSPORTE Y DISTRIBUCI | | | SCAC4 |
| 2440 | SDPE | SHERDIL PRECISION | | | SCAC4 |
| 2441 | SDPF | S D PERFORMANCE INC | | | SCAC4 |
| 2442 | SDPG | SDI EXPRESS | | | SCAC4 |
| 2443 | SDPJ | SOUND PETROLEUM II INC | | | SCAC4 |
| 2444 | SDPK | SPECIAL DISPATCH OF KANSAS CITY, INC | | | SCAC1 |
| 2445 | SDPK | SIDHU, P S TRUCKING LTD | | | SCAC4 |
| 2446 | SDPM | SPECIAL DISTRIBUTION PHOENIX LLC | | | SCAC4 |
| 2447 | SDPN | STEIKAR TRUCKING LIMITED | | | SCAC4 |
| 2448 | SDPR | SD TRANSPORTATION | | | SCAC4 |
| 2449 | SDPS | SPECIAL DISPATCH OF SAN ANTONIO INC | | | SCAC4 |
| 2450 | SDPSV | Southdown PSV | City: Copthorne | GB | TRAFFIC |
| 2451 | SDPT | SEAMODAL TRANSPORT CORPORATION | | | SCAC4 |
| 2452 | SDPV | SAPUTO DAIRY PRODUCTS CANADA GP | | | SCAC4 |
| 2453 | SDPX | South Dakota Soybean Processors, Inc. | added 4/1997; eliminated 1/1999; added 7/2000; 7/2000; eliminated 10/2001; added 1/2003; eliminated 1/2004 | | NAKINA |
| 2454 | SDPX | South Dakota Soybean Processors, LLC | added 1/2004; 7/2005 | | NAKINA |
| 2455 | SDPX | South Dakota Soybean Processors, Inc. | added 4/97; eliminated 1/99; added 7/2000; 7/2000 | | NRHS |
| 2456 | SDPX | SOUTH DAKOTA SOYBEAN PROCESSORS | | | PWRC |
| 2457 | SDPX | South Dakota Soybean Processors | | | RSRV |
| 2458 | SDPX | SOUTH DAKOTA SOYBEAN PROCESSORS LLC | | | SCAC4 |
| 2459 | SDPY | SPEEDY TRANSPORTATION LLC | | | SCAC4 |
| 2460 | SDQ | Servicio y Mantenimiento Tecnico DQ, S.A. de C.V. | | MEX | AVCODES |
| 2461 | SDQC | SD LOGISTICS LLC | | | SCAC4 |
| 2462 | SDQD | SOUTHEAST CONSOLIDATORS INC (DALLAS | | | SCAC4 |
| 2463 | SDQJ | STD LOGISTICS LTD | | | SCAC4 |
| 2464 | SDQL | SANDIA OIL COMPANY | | | SCAC4 |
| 2465 | SDQM | SPEEDM | | | SCAC4 |
| 2466 | SDQN | SOUTHEAST CONSOLIDATORS INC (DALLAS | | | SCAC4 |
| 2467 | SDQS | SDS INC | | | SCAC4 |
| 2468 | SDQT | SOUTHEAST CONSOLIDATORS INC (DALLAS | | | SCAC4 |
| 2469 | SDR | Air Toronto | IATA: CS, Callsign: Soundair, Air Canada Connector | CDN | AVCODES |
| 2470 | SDR | City Airline AB | IATA: CF, Callsign: Swedestar, IATA Prefix: 419, Ceased Operations and filed for bankruptcy 12 May 2012. | S | AVCODES |
| 2471 | SDR | Soundair Express | Callsign: Soundiar, | CDN | AVCODES |
| 2472 | SDR | Sundair GmbH | IATA: SR, Callsign: Sundair, Commenced operations on 27 September 2017. | D | AVCODES |
| 2473 | SDR | City Airline | IATA: CF | | ICAO1 |
| 2474 | SDR | Sudarec | | RO | TRAFFIC |
| 2475 | SDRA | STRADER-FERRIS INTERNATIONAL LIMITE | | | SCAC4 |
| 2476 | SDRA | Sundair | Real: SDR | D | TRAFFIC |
| 2477 | SDRC | SISTEMA DE RIEGO EL DURAZNO | | | SCAC4 |
| 2478 | SDRD | SANDER GEOPHYSICS LTD | | | SCAC4 |
| 2479 | SDRE | SERVICE DE REMORQUAGE DIRECT INC | | | SCAC4 |
| 2480 | SDRH | SMITH, D R TRUCKING INC | | | SCAC4 |
| 2481 | SDRI | SISTEMA DE RIEGO PETERS SA DE CV | | | SCAC4 |
| 2482 | SDRO | SUDDATH RELOCATION SYSTEMS OF ST PE | | | SCAC4 |
| 2483 | SDRR | SOUTH DAKOTA RAILROAD AUTHORITY | | | PWRC |
| 2484 | SDRS | SANDERS TRUCK TRANSPORTATION CO INC | | | SCAC4 |
| 2485 | SDRT | SNADER, D L TRANSPORT INC | | | SCAC4 |
| 2486 | SDRU | SIDRA DENIZCILIK VE TICARET A.S. | | TR | BIC |
| 2487 | SDRV | SADDLE RIVER TRAILS INC | | | SCAC4 |
| 2488 | SDRW | SANDERS, WILEY TRUCK LINES INC | | | SCAC4 |
| 2489 | SDRX | Sinclair Refining Co. | 8/1920-7/1954; eliminated 1/1958 | | NAKINA |
| 2490 | SDRX | Union Tank Car Co. | 10/1957; added 1/1958; 4/1961-4/1970; eliminated 7/1973 | | NAKINA |
| 2491 | SDRX | Central Puget Sound Regional Transit Authority | 7/2000-7/2005 (not listed) | | NAKINA |
| 2492 | SDRX | Sinclair Refining Co. | 4/38-1/52; eliminated 1/58 | | NRHS |
| 2493 | SDRX | Union Tank Car Co. | 10/57; added 1/58; 4/61-4/70; eliminated 7/73 | | NRHS |
| 2494 | SDRX | Central Puget Sound Regional Transit Authority | Jul-00 | | NRHS |
| 2495 | SDRX | *SINCLAIR REFINING CO. (UNION TANK CAR CO.) | | | PWRC |
| 2496 | SDRX | +CENTRAL PUGET SOUND REGIONAL TRANSIT AUTHORITY (SEATTLE) | | | PWRC |
| 2497 | SDRX | Sounder Commuter Rail | | | RSRV |
| 2498 | SDRX | CENTRAL PUGET SOUND REGIONAL TRANSI | | | SCAC4 |
| 2499 | SDRX | Sinclair Refining Co. | | USA | TRAFFIC |
| 2500 | SDS | CAA Training Standards | Callsign: Standards, | GB | AVCODES |
