| 2301 | SDIK | SKYCO DISTRIBUTION INC | | | SCAC4 |
| 2302 | SDIM | SCHUMM, DAVID INC | | | SCAC4 |
| 2303 | SDIQ | SD INCORPORATED | | | SCAC4 |
| 2304 | SDIS | STANDISH TRANSPORT | | | SCAC4 |
| 2305 | SDIT | San Diego & Imperial Valley Ry. Co. | added 10/1984 | | NAKINA |
| 2306 | SDIT | San Diego & Imperial Valley Ry. Co. | added 10/84 | | NRHS |
| 2307 | SDIT | SAN DIEGO & IMPERIAL VALLEY RWY. CO. | | | PWRC |
| 2308 | SDIT | SEDITA TRUCKING INC | | | SCAC4 |
| 2309 | SDIV | SAN DIEGO & IMPERIAL VALLEY RAILROAD (EXPIRED) | | | PWRC |
| 2310 | SDIV | San Diego and Imperial Valley Railroad | | | RSRV |
| 2311 | SDIV | SPECIAL DISTRIBUTION SERVICES INC | | | SCAC4 |
| 2312 | SDIW | SHEPPARDWOOD DISTRIBUTORS | | | SCAC4 |
| 2313 | SDIX | Smith-Douglass Co., Inc. | 4/1947-7/1954; eliminated 4/1957 | | NAKINA |
| 2314 | SDIX | Steel Dynamics, Inc. | 7/2005 (not listed) | | NAKINA |
| 2315 | SDIX | Smith-Douglass Co., Inc. | 1/52; eliminated 4/57 | | NRHS |
| 2316 | SDIX | *SMITH-DOUGLAS CO., INC. | | | PWRC |
| 2317 | SDIX | *SOUTH DAKOTA & IOWA RAILROAD | | | PWRC |
| 2318 | SDIX | +STEEL DYNAMICS, INC. | | | PWRC |
| 2319 | SDIX | STEEL DYNAMICS INC | | | SCAC4 |
| 2320 | SDIY | San Diego & Imperial Valley R.R. Co. | eliminated 10/1992; 1/1994-7/2005 | | NAKINA |
| 2321 | SDIY | San Diego & Imperial Valley R.R. Co. | eliminated 10/92; 1/94-7/2000 | | NRHS |
| 2322 | SDIY | SAN DIEGO & IMPERIAL VALLEY RAILROAD CO.,INC. | | | PWRC |
| 2323 | SDIY | San Diego and Imperial Valley Railroad | | | RSRV |
| 2324 | SDIY | SAN DIEGO AND IMPERIAL VALLEY RAILROAD | | | SCAC1 |
| 2325 | SDIY | SAN DIEGO & IMPERIAL VALLEY RAILROA | | | SCAC4 |
| 2326 | SDIY | San Diego & Imperial Valley | | USA | TRAFFIC |
| 2327 | SDJ | Club 328 Ltd | Callsign: Spacejet, Ceased operations. | GB | AVCODES |
| 2328 | SDJ | Club 328 | | | ICAO1 |
| 2329 | SDJ | Södra Dalarnas Järnväg | 1881 - 1948 | S | svenska-lok.se |
| 2330 | SDJA | STUTZ DRAYAGE LLC | | | SCAC4 |
| 2331 | SDJC | SMEARER, D J INC | | | SCAC4 |
| 2332 | SDJG | SMITH, D J TRUCKING | | | SCAC4 |
| 2333 | SDJI | SALYER, D J INC | | | SCAC4 |
| 2334 | SDJM | SUAREZ DAVILA, JUAN | | | SCAC4 |
| 2335 | SDJN | STEWART DELL INC | | | SCAC4 |
| 2336 | SDJR | STEED BROS INC | | | SCAC4 |
| 2337 | SDJR | Somerset and Dorset Joint Railway | The Somerset & Dorset Joint Railway, also known as the S&D, was an English railway line connecting Bath (in north-east Somerset) and Bournemouth (now in south-east Dorset but then in Hampshire), with a branch from Evercreech Junction to Burnham-on-Sea and Bridgwater. Strictly speaking, the main line ran from Bath Junction to Broadstone, as the line between Broadstone and Bournemouth was owned by the London and South Western Railway, while the line between Bath Junction and Bath was owned by the Midland Railway. | GB | TRAFFIC |
| 2338 | SDJS | STEWART, DOUGLAS SCOTT | | | SCAC4 |
| 2339 | SDK | SADELCA - Sociedad Aerea Del Caqueta | | | ICAO1 |
| 2340 | SDKB | SCHMIDT, T A TRUCKING INC | | | SCAC4 |
| 2341 | SDKD | SCHROEDER, D TRUCKING | | | SCAC4 |
| 2342 | SDKD | SD - Kolejová doprava, a.s. | | CZ | VKM |
| 2343 | SDKE | SANDERS TRUCKING SERVICE | | | SCAC4 |
| 2344 | SDKJ | SEED TRUCKING | | | SCAC4 |
| 2345 | SDKK | SUNLAND TRUCKING INC | | | SCAC4 |
| 2346 | SDKM | SANDRIN SERVICES INC | | | SCAC4 |
| 2347 | SDKN | STANLEY, D K TRUCKING INC | | | SCAC4 |
| 2348 | SDKO | SANDAL TRUCKING INC | | | SCAC4 |
| 2349 | SDKP | SUPER DECK TRANSPORT | | | SCAC4 |
| 2350 | SDKQ | SPEEDMA | | | SCAC4 |
| 2351 | SDKR | SNEDEKER TRANSPORTATION | | | SCAC4 |
| 2352 | SDKS | SHEPARD & KEMNA LEASING LLC | | | SCAC4 |
| 2353 | SDKV | SLADEK TRUCKING SERVICES LLC | | | SCAC4 |
| 2354 | SDKW | S & D TRUCKING INC | | | SCAC4 |
| 2355 | SDL | Skydrift Ltd. | Callsign: Skydrift, Name changed from Skydrift Aircharter. ICAO designator changed from DFT | GB | AVCODES |
| 2356 | SDL | Skydrift | | | ICAO1 |
| 2357 | SDL | Siemens Dispolok GmbH | München | D | privat-bahn.de |
| 2358 | SDLA | SAMCO DELTA LTD | | | SCAC4 |
| 2359 | SDLB | S & D LLC | | | SCAC4 |
| 2360 | SDLC | SADDLE CREEK TRANSPORTATION INC | | | SCAC4 |
| 2361 | SDLE | STRUCTURES D L D LTEE | | | SCAC4 |
| 2362 | SDLG | SODREL LOGISTICS LLC | | | SCAC4 |
| 2363 | SDLH | SEA & LAND SHIPPING INC | | | SCAC4 |
| 2364 | SDLJ | SEIDL, L E JR TRUCKING LLC | | | SCAC4 |
| 2365 | SDLL | SCHERADELLA TRUCKING | | | SCAC4 |
| 2366 | SDLM | SLIDELL MOVING | | | SCAC4 |
| 2367 | SDLO | SMITH, DENNIS LOGGING | | | SCAC4 |
| 2368 | SDLP | SILVA DE LA PORTILLA, RAYMUNDO | | | SCAC4 |
| 2369 | SDLR | SADLER, RANDY J | | | SCAC4 |
| 2370 | SDLS | SMITH DRAY LINE & STORAGE CO INC | | | SCAC4 |
| 2371 | SDLT | SHORT, DONALD L TRUCKING INC | | | SCAC4 |
| 2372 | SDLV | SILKENSTONE DECOR LTD | | | SCAC4 |
| 2373 | SDLW | STAFFORD, L E TRUCKING LLC | | | SCAC4 |
| 2374 | SDLY | SPEEDLINE SYSTEMS INC | | | SCAC4 |
| 2375 | SDM | State Transport Company of Russia | IATA: R4, Callsign: Russia, IATA Prefix: 948, Merged with Pulkovo Aviation Enterprise FV/PLK. Designator R4 reinstated by IATA | RUS | AVCODES |
| 2376 | SDM | Rossiya Airlines Open JSC | IATA: FV, Callsign: Russia, IATA Prefix: 195, Formed by the merger of Pulkovo Aviation Enterprise and State Transport Company of Russia. | RUS | AVCODES |
| 2377 | SDM | Rossiya Airlines JSC | IATA: FV, Callsign: Rossiya, IATA Prefix: 195, ICAO Callsign changed from Russia. Formed by the merger of Pulkovo Aviation Enterprise and State Transport Company of Russia. | RUS | AVCODES |
| 2378 | SDM | Rossiya | IATA: FV | | ICAO1 |
| 2379 | SDMC | SLEDMAS | | | SCAC4 |
| 2380 | SDMD | STARS DE MEXICO | | | SCAC4 |
| 2381 | SDME | STARKEY DE MEXICO S A DE C V | | | SCAC4 |
| 2382 | SDMI | SANDOVAL MENDOZA, MIGUEL | | | SCAC4 |
| 2383 | SDMJ | SCHMIDT, SAM MOTORSPORTS LLC | | | SCAC4 |
| 2384 | SDMK | SPEEDMA | | | SCAC4 |
| 2385 | SDMN | SERVICIOS DE EMPAQUE Y MUDANZAS INT | | | SCAC4 |
| 2386 | SDMO | SELDON SMITH & SONS LTD | | | SCAC4 |
| 2387 | SDMQ | SAND MOUNTAIN INC | | | SCAC4 |
| 2388 | SDMS | STANDARD MOVING & STORAGE INC | | | SCAC4 |
| 2389 | SDMU | MARS COMPANY | | J | BIC |
| 2390 | SDMX | The D.M. Sears Co., Inc. | 7/1932 | | NAKINA |
| 2391 | SDMX | D. M. SEARS CO., INC. | | | PWRC |
| 2392 | SDMY | SEADREA | | | SCAC4 |
| 2393 | SDN | Spirt of Africa Airlines | Callsign: Falair, ICAO Callsign changed to Blue Nile | SUD | AVCODES |
| 2394 | SDN | Spirt of Africa Airlines | Callsign: Blue Nile, ICAO Callsign changed from Falair | SUD | AVCODES |
| 2395 | SDN | Spirit of Africa Airlines | | | ICAO1 |
| 2396 | SDN | Schwaben Dampf Neuoffingen e.V. | Neuoffingen | D | privat-bahn.de |
| 2397 | SDN | Schwaben Dampf e.V. | | DE | VKM |
| 2398 | SDNA | SCERNI DI NAVIGAZIONE S R L | | | SCAC4 |
| 2399 | SDNB | SPECIAL DISTRIBUTION MARYLAND LLC | | | SCAC4 |
| 2400 | SDND | SUDDEN IMPACT RACING LLC | | | SCAC4 |
