| 2201 | MDRY | Madison Ry. Co., Inc. | added 1/78; eliminated 1/79 | | NRHS |
| 2202 | MDRY | *MADISON RWY. CO. | | | PWRC |
| 2203 | MDRY | *RETIRED 08-21-91 ATP (0468) | | | PWRC |
| 2204 | MDRY | *MIDLANDS RAILWAY | | | PWRC |
| 2205 | MDS | Med Airlines S.p.A. | IATA: M8, Callsign: Mizar, Ceased operations on 15 March 2001. | I | AVCODES |
| 2206 | MDS | McNeely Charter Services, Inc. | Callsign: Mid-South, | USA | AVCODES |
| 2207 | MDS | McNeely Charter Services | | | ICAO1 |
| 2208 | MDS | Meridian Southern Ry., L.L.C. | 7/2000-7/2005; added 7/2006 | | NAKINA |
| 2209 | MDS | Meridian Southern Ry., L.L.C. | Jul-00 | | NRHS |
| 2210 | MDS | MERIDIAN SOUTHERN RAILWAY [MACON, DUBLIN & SAVANNAH RR] | | | PWRC |
| 2211 | MDS | Meridian Southern Railway | | | RSRV |
| 2212 | MDS | MERIDIAN SOUTHERN RAILWAY LLC | | | SCAC4 |
| 2213 | MDSB | Burlington Northern Inc. | 1/1980 | | NAKINA |
| 2214 | MDSB | Burlington Northern Inc. | Jan-80 | | NRHS |
| 2215 | MDSB | BNSF {BURLINGTON NORTHERN RAILROAD] | | | PWRC |
| 2216 | MDSB | BNSF Railway | | | RSRV |
| 2217 | MDSB | MUKARNAS DENIZCILIK SAN VE TIC LTD | | | SCAC4 |
| 2218 | MDSC | MCCHAIN DISTRIBUTION SYSTEMS INC | | | SCAC4 |
| 2219 | MDSD | MAGNUM DIVERSIFIED SERVICES INC | | | SCAC4 |
| 2220 | MDSE | MCKENNAH DISTRIBUTION SERVICES INC | | | SCAC4 |
| 2221 | MDSH | MIDSHIP MARITIME S A | | | SCAC4 |
| 2222 | MDSI | MID-STATE MOVING & STORAGE CO INC | | | SCAC4 |
| 2223 | MDSJ | MALL DELIVERY SERVICE INC | | | SCAC4 |
| 2224 | MDSK | MID STATES PACKAGING INC | | | SCAC4 |
| 2225 | MDSL | MICKEY D & SON LLC | | | SCAC4 |
| 2226 | MDSN | MADISON TERMINAL RAILWAY LLC | | | SCAC4 |
| 2227 | MDSP | MDS EXPRESS LTD | | | SCAC4 |
| 2228 | MDSPB | Mestská dopravná spoločnosť, a.s., Považská Bystrica | | SK | TRAFFIC |
| 2229 | MDSR | MANNING DISTRIBUTION SERVICES INC | | | SCAC4 |
| 2230 | MDSS | MID SOUTH SALES INC | | | SCAC4 |
| 2231 | MDST | MIDSTATES TRUCKING COMPANY INC | | | SCAC4 |
| 2232 | MDSU | QINETIQ TARGET SYSTEMS LIMITED | | GB | BIC |
| 2233 | MDSU | MONDIA KIRWAN S.A. | | | SCAC4 |
| 2234 | MDSV | MEDICAL DELIVERY SERVICES INC | | | SCAC4 |
| 2235 | MDSX | Merchants Despatch Transportation Co. | added 4/1953; 7/1954; eliminated 1/1955; added 7/1955; eliminated 1/1956 | | NAKINA |
| 2236 | MDSX | Merchants Despatch Transportation Co. | added 7/55 | | NRHS |
| 2237 | MDSX | MERCHANTS DESPATCH TRANSPORTATION CORP. | | | PWRC |
| 2238 | MDSY | MID STATE SYSTEMS INC | | | SCAC4 |
| 2239 | MDSZ | MEDSPAN SHIPPING SERVICE INC | | | PWRC |
| 2240 | MDSZ | Medspan Shipping Service | | | RSRV |
| 2241 | MDSZ | MEDSPAN SHIPPING SERVICE INC | | | SCAC4 |
| 2242 | MDT | Sundt Air | Callsign: Midnight, ICAO designator changed from NOO / Name changed from Nor Aviation A/S 01 July 2000. | N | AVCODES |
| 2243 | MDT | Air Mediterranee Compagnie | Callsign: Air Mediter, | F | AVCODES |
| 2244 | MDT | Sundt Air | | | ICAO1 |
| 2245 | MDT | Merchants Despatch Transportation Co. | 7/1937-1/1980; eliminated 1/1983 | | NAKINA |
| 2246 | MDT | Merchants Despatch Refrigerator Line (Merchants Despatch, Inc.) | 7/1923; 7/1935 | | NAKINA |
| 2247 | MDT | Merchants Despatch Transportation Co. | 4/38-1/80; eliminated 1/83 | | NRHS |
| 2248 | MDT | *MERCHANTS DESPATCH TRANSPORTATION CORP. | | | PWRC |
| 2249 | MDT | *MARYLAND DEPARTMENT OF TRANSPORTATION | | | PWRC |
| 2250 | MDT | Merchants Despatch Transportation Corporation | | | RSRV |
| 2251 | MDT | Merchant Despatch Transportation | | USA | TRAFFIC |
| 2252 | MDTA | MIDLAND TRANSPORTATION CO | | | SCAC1 |
| 2253 | MDTA | MITTELSTADT TRUCKING LLC | | | SCAC4 |
| 2254 | MDTB | M D TRANSPORT CO LTD | | | SCAC4 |
| 2255 | MDTF | MEDINAS TRANSFER | | | SCAC4 |
| 2256 | MDTG | MISTER D TRUCKING INC | | | SCAC4 |
| 2257 | MDTI | M & D TRUCKING | | | SCAC4 |
| 2258 | MDTK | MUTHLER, DAN TRUCKING | | | SCAC4 |
| 2259 | MDTL | MARDOT LOGISTICS INC | | | SCAC4 |
| 2260 | MDTP | MCDERMID TRANSPORTATION INC | | | SCAC4 |
| 2261 | MDTQ | MCDERMOTT, D T TRUCKING INC | | | SCAC4 |
| 2262 | MDTR | MEADE TRUCKING COMPANY INC | | | SCAC4 |
| 2263 | MDTS | MODERN TRANSPORTATION SERVICES INC | | | SCAC4 |
| 2264 | MDTT | MAINE DEPARTMENT OF TRANSPORTATION | | | PWRC |
| 2265 | MDTU | M ROMEU SL | | | SCAC4 |
| 2266 | MDTV | MEDINA TRAFFIC SERVICES INC | | | SCAC4 |
| 2267 | MDTW | MEYER, DOUG TRUCKING INC | | | SCAC4 |
| 2268 | MDTX | Southern Region Industrial Realty, Inc. | added 7/1999; 7/2000-7/2005 | | NAKINA |
| 2269 | MDTX | Merchants Despatch Transportation Corp. | added 7/1989; 1/1994; eliminated 7/1999 | | NAKINA |
| 2270 | MDTX | Merchants Despatch Transportation Co., series 30000-31099 (Merchants Despatch, Inc.) | 7/1923 | | NAKINA |
| 2271 | MDTX | Merchants Despatch Transportation Co. (New York Central R.R.) | 8/1920 | | NAKINA |
| 2272 | MDTX | Merchants Despatch Transportation Corp. | added 7/89; 1/94; eliminated 7/99 | | NRHS |
| 2273 | MDTX | Southern Region Industrial Realty, Inc. | added 7/99; 7/2000 | | NRHS |
| 2274 | MDTX | *MERCHANTS DESPATCH TRANSPORTATION CORP. (NEW YORK CENTRAL RAILROAD) | | | PWRC |
| 2275 | MDTX | +MERCHANTS DESPATCH TRANSPORTATION CORP. (SOUTHERN REGION INDUSTRIAL REALTY, INC.) | | | PWRC |
| 2276 | MDTX | *MOUNT DORA, TAVARES, EUSTIS RAILROAD | | | PWRC |
| 2277 | MDTX | Merchants Despatch Refrigerator Line | | | RSRV |
| 2278 | MDTX | SOUTHERN REGION INDUSTRIAL REALTY I | | | SCAC4 |
| 2279 | MDTZ | MISTEC | | | PWRC |
| 2280 | MDUC | MCDANIEL TRUCKING COMPANY | | | SCAC4 |
| 2281 | MDUP | MCDUFFIE AUTO TRANSPORT | | | SCAC4 |
| 2282 | MDUR | MEADS, ARTHUR R | | | SCAC4 |
| 2283 | MDUT | MILLER, DOUG TRUCKING INC | | | SCAC4 |
| 2284 | MDUU | MDU MAIN-DONAU-UMSCHLAGS-TRANSPORT-GMBH | | D | BIC |
| 2285 | MDUX | Montana-Dakota Utilties Co. | 1/1945-1/1950 | | NAKINA |
| 2286 | MDUX | MONTANA-DAKOTA UTILITIES CO. | | | PWRC |
| 2287 | MDV | Moldavian Airlines | IATA: 2M, Callsign: Moldavian, IATA Prefix: 860, Established on 26 July 1994. Commenced operations on 19 August 1994. Ceased operations during 2014. | MD | AVCODES |
| 2288 | MDV | Moldavian Airlines | IATA: 2M | | ICAO1 |
| 2289 | MDV | Maryland, Delaware & Virginia Ry. Co. (Penna. Ry. System) | 8/1920-7/1923 | | NAKINA |
| 2290 | MDV | PENNSYLVANIA RWY. SYSTEM [MARYLAND, DELAWARE & VIRGINIA RWY. CO.] | | | PWRC |
| 2291 | MDVA | MORNING DOVE SERVICES LLC | | | SCAC4 |
| 2292 | MDVC | MARITIME DELIVERY SERVICES INC | | | SCAC4 |
| 2293 | MDVD | MCDONALD, DAVID STEVE | | | SCAC4 |
| 2294 | MDVE | MARITIME DELIVERY SERVICES (CANADA) | | | SCAC4 |
| 2295 | MDVH | MOVERS DISPATCH INC | | | SCAC4 |
| 2296 | MDVU | MALDIVES STATE SHIPPING (MSS) | | MV | BIC |
| 2297 | MDVW | MIDWEST TRANSPORT SERVICES INC | | | SCAC4 |
| 2298 | MDVY | MIKES DELIVERY INC | | | SCAC4 |
| 2299 | MDW | Midway Airlines | IATA: JI, Callsign: Midway, IATA Prefix: 878, Suspended operations on 17 July 2002. | USA | AVCODES |
| 2300 | MDW | Flyawesome Limited | Callsign: Medwing, Name changed from Flyawesome Holdings Limited. ICAO designator changed from FMB. ICAO Callsign changed from Rescue JEt. | M | AVCODES |
