| 4601 | MKLN | MAERSK LINE LIMITED | | | SCAC4 |
| 4602 | MKLP | MERKEL, PERRY D INC | | | SCAC4 |
| 4603 | MKLU | MEDKON LINES | | TR | BIC |
| 4604 | MKLY | MARKLEY TRANSPORT | | | SCAC4 |
| 4605 | MKM | Mediterranean Express Ltd | Ceased operations. | M | AVCODES |
| 4606 | MKMB | MIKES MOBILE HOME REPAIR INC | | | SCAC4 |
| 4607 | MKMC | MKM DISTRIBUTION SERVICES INC | | | SCAC4 |
| 4608 | MKMD | MACKIE MOVING SYSTEMS CORPORATION ( | | | SCAC4 |
| 4609 | MKMI | MKM TRANSPORTATION CO | | | SCAC4 |
| 4610 | MKMK | MICHAL KM TRUCKING INC | | | SCAC4 |
| 4611 | MKML | MILL CREEK METALS LLC | | | SCAC4 |
| 4612 | MKMQ | MARAN TANKERS MANAGEMENT INC | | | SCAC4 |
| 4613 | MKMS | MACKIE MOVING SYSTEMS CORPORATION | | | SCAC4 |
| 4614 | MKMV | MARKS MOVERS & STORAGE INC | | | SCAC4 |
| 4615 | MKN | Mekong Airlines Co. Ltd. | IATA: M8, Callsign: Mekong Airlines, Ceased Operations in October 2003. Name changed from Yana Airlines Co. Ltd. | K | AVCODES |
| 4616 | MKN | Mekong Airlines | | | ICAO1 |
| 4617 | MKNA | MCKONNEN AUTO CARRIERS | | | SCAC4 |
| 4618 | MKNC | MONTANI TRUCKING INC | | | SCAC4 |
| 4619 | MKND | MCKEND | | | SCAC4 |
| 4620 | MKNE | MACKENZIE | | | SCAC4 |
| 4621 | MKNG | MACCHIA TRUCKING | | | SCAC1 |
| 4622 | MKNL | MCKINLEY TRUCKING CO INC | | | SCAC4 |
| 4623 | MKNN | MACKINNON, RUSSELL J | | | SCAC4 |
| 4624 | MKNO | MACKINNON TRANSPORT INC | | | SCAC4 |
| 4625 | MKNR | Mackenzie Northern Railway | | | RSRV |
| 4626 | MKNT | MCKINNEY TRAILER RENTAL | | | SCAC4 |
| 4627 | MKNW | MT. KISCO-NEW YORK EXPRESS CO | | | SCAC1 |
| 4628 | MKNW | MOUNT KISCO-NEW YORK EXPRESS CO, IN | | | SCAC4 |
| 4629 | MKO | Markoss Aviation Ltd. | Callsign: Goshawk, | GB | AVCODES |
| 4630 | MKO | Markoss Aviation | | | ICAO1 |
| 4631 | MKO | Museumseisenbahn Küstenbahn Ostfriesland e.V. | Norden | D | privat-bahn.de |
| 4632 | MKOA | MAKO LINES INC | | | SCAC4 |
| 4633 | MKOC | MACLASKE | | | SCAC4 |
| 4634 | MKOD | MANKO DELIVERY SYSTEMS INC | | | SCAC4 |
| 4635 | MKOE | MARKO EXPRESS | | | SCAC4 |
| 4636 | MKOF | MEIKO FREIGHT SERVICE, INC | | | SCAC1 |
| 4637 | MKOI | MCKINLEY OIL LLC | | | SCAC4 |
| 4638 | MKON | Miejski Zakład Komunikacji w Koninie sp. z o.o. | | PL | TRAFFIC |
| 4639 | MKontJ | Malmö - Kontinentens Järnväg | 1897 - 1909 | S | svenska-lok.se |
| 4640 | MKOR | MARKO TRANSPORTATION | | | SCAC4 |
| 4641 | MKOT | MEIKO TRANS CO LTD | | | SCAC4 |
| 4642 | MKOU | METIN AKDURAK LTD | | | SCAC4 |
| 4643 | MKP | Adygeya-Avia, Joint-Stock Company | Callsign: Adygeya, | RUS | AVCODES |
| 4644 | MKPC | MARKETPLAC | | | SCAC4 |
| 4645 | MKPM | MARKO PETROLEUM | | | SCAC4 |
| 4646 | MKPX | Campbell Soup Co., Central Division | 1/1945-4/1947 | | NAKINA |
| 4647 | MKPX | Meyer Kornblum Refrigerator Car Co. | 7/1937-1/1943 | | NAKINA |
| 4648 | MKPX | Meyer Kornblum Packing Co. (Merchants Despatch, Inc.) | 7/1935 | | NAKINA |
| 4649 | MKPX | Meyer Kornblum Refrigerator Car Co. | Apr-38 | | NRHS |
| 4650 | MKPX | *MEYER KORNBLUM REFRIGERATOR CAR CO. | | | PWRC |
| 4651 | MKPX | *CAMPBELL SOUP CO., CENTRAL DIVISION | | | PWRC |
| 4652 | MKQL | MAKTRANS LOGISTICS INC | | | SCAC4 |
| 4653 | MKQT | MARK'S TRUCKING COMPANY | | | SCAC1 |
| 4654 | MKQT | MARKS TRUCKING COMPANY | | | SCAC4 |
| 4655 | MKQU | M A K CONTAINER LINE LLC | | UAE | BIC |
| 4656 | MKR | Lanmei Airlines (Cambodia) Co., Ltd. | IATA: LQ, Callsign: Air Lanme, IATA Prefix: 961, AOC granted and due to commence operations on 09 October 2017. | K | AVCODES |
| 4657 | MKRG | MACKAY | | | SCAC4 |
| 4658 | MKRI | MARKER INDUSTRIES INC | | | SCAC4 |
| 4659 | MKRK | MIREKS TRUCKING INC | | | SCAC4 |
| 4660 | MKRP | MAK TRANSPORT CO | | | SCAC4 |
| 4661 | MKRQ | MAKRON SHIPPING LIMITED | | | SCAC4 |
| 4662 | MKRS | MIKES TRANSPORT INC | | | SCAC4 |
| 4663 | MKRT | MAKI TRUCKING & LOGGING | | | SCAC4 |
| 4664 | MKRU | LLC MAKRA LOGISTICS | | RUS | BIC |
| 4665 | MKRU | TRASPETROL SERVICE SRL | | | SCAC4 |
| 4666 | MKRV | MACK RELOCATION SERVICES | | | SCAC4 |
| 4667 | MKRX | McKean County Refining Co. | 7/1930 | | NAKINA |
| 4668 | MKRX | *MCKEAN COUNTY REFINING CO. | | | PWRC |
| 4669 | MKRX | *MK RAIL CORPORATION | | | PWRC |
| 4670 | MKS | Pimichikamac Air Ltd. | Callsign: Mikisew, | CDN | AVCODES |
| 4671 | MKS | Pimichikamac Air | | | ICAO1 |
| 4672 | MKSD | MARKIAN STUDIOS INC | | | SCAC4 |
| 4673 | MKSDEB | Miejska Komunikacja Samochodowa sp. z o.o. w Dêbicy | | PL | TRAFFIC |
| 4674 | MKSG | MATAKANA SCAFFOLDING BC INC | | | SCAC4 |
| 4675 | MKSI | MATLOCK & SONS INC | | | SCAC4 |
| 4676 | MKSK | MCKISSIC | | | SCAC4 |
| 4677 | MKSL | MIKE'S TRUCKING LLC | | | SCAC4 |
| 4678 | MKSN | MKS CONTRACTORS INC | | | SCAC4 |
| 4679 | MKSO | MARKIS LOGISTICS LLC | | | SCAC4 |
| 4680 | MKSP | M K SERVICES | | | SCAC4 |
| 4681 | MKSR | MARK SERVICES INC | | | SCAC4 |
| 4682 | MKSSK | MKS Skarżysko-Kamienna | | PL | TRAFFIC |
| 4683 | MKSU | MARTIN KNOLL | | | SCAC4 |
| 4684 | MKSW | MARKS TRANSPORTATION INC | | | SCAC4 |
| 4685 | MKT | Union Pacific R.R. Co. | added 4/1997; 7/2000-7/2005 | | NAKINA |
| 4686 | MKT | Missouri Pacific System | added 1/1990; 1/1994; eliminated 4/1997 | | NAKINA |
| 4687 | MKT | Missouri-Kansas-Texas R.R. Co. | 1/1941-10/1966 & 1/1975-1/1980; eliminated 1/1990 | | NAKINA |
| 4688 | MKT | Missouri-Kansas-Texas R.R. Co. | 1/52-10/66 & 1/75-1/80; eliminated 1/90 | | NRHS |
| 4689 | MKT | Missouri Pacific System | added 1/90; 1/94; eliminated 4/97 | | NRHS |
| 4690 | MKT | Union Pacific R.R. Co. | added 4/97; 7/2000 | | NRHS |
| 4691 | MKT | UNION PACIFIC RAILROAD CO. [MISSOURI PACIFIC; MISSOURI, KANSAS & TEXAS RWY.; M.K. & T. LINES} | | | PWRC |
| 4692 | MKT | Missouri-Kansas-Texas Railroad (Union Pacific Railroad) | | | RSRV |
| 4693 | MKT | Missouri-Kansas-Texas Railroad Company | | USA | TRAFFIC |
| 4694 | MKT | Majkoltrans Sp. Z o.o. | | PL | VKM |
| 4695 | MKTB | MCKENZIE TRUCKING CO | | | SCAC4 |
| 4696 | MKTC | MACK TRUCKING | | | SCAC4 |
| 4697 | MKTJ | MK TRUCKING | | | SCAC4 |
| 4698 | MKTK | MANKE TRUCKING, INC | | | SCAC1 |
| 4699 | MKTK | MANKE TRUCKING INCORPORATED | | | SCAC4 |
| 4700 | MKTL | MACKIE TRANSPORT LIMITED (DIV OF MA | | | SCAC4 |
