| 3001 | KLOSOK | Przedsiębiorstwo Produkcyjno-Usługowo-Handlowe „Kłosok” Andrzej Kłosok | | PL | TRAFFIC |
| 3002 | KLOT | KLOS TRUCKING INC | | | SCAC4 |
| 3003 | KLOU | KLOIBER GMBH | | D | BIC |
| 3004 | KLOU | KLOIBER GMBH | | | SCAC4 |
| 3005 | KLOW | KLOCKWERKS | | | SCAC4 |
| 3006 | KLOY | KLR LOGISTICS | | | SCAC4 |
| 3007 | KLP | Przedsiębiorstwo Usług Kolejowych KOLPREM Sp. z o.o. | | PL | VKM |
| 3008 | KLPC | KLAPEC, J BERNARD | | | SCAC3 |
| 3009 | KLPC | KLAPEC TRUCKING COMPANY | | | SCAC4 |
| 3010 | KLPD | KLEPPER, DICK TRUCKING LTD | | | SCAC4 |
| 3011 | KLPI | KL PRODUCTS INC | | | SCAC4 |
| 3012 | KLPL | KLIPPEL CARRIER CO | | | SCAC3 |
| 3013 | KLPM | KELSO PANAMA SA | | | SCAC3 |
| 3014 | KLPP | KLOPP, ROBERT | | | SCAC3 |
| 3015 | KLPT | KLEPPER TRUCKING INC | | | SCAC3 |
| 3016 | KLQL | KOOL LOGISTICS LLC | | | SCAC4 |
| 3017 | KLR | Columbus Air Transport, Inc. | Callsign: Kay-Ler, | USA | AVCODES |
| 3018 | KLR | Columbus Air Transport | | | ICAO1 |
| 3019 | KLRB | KILROY BROS INC | | | SCAC3 |
| 3020 | KLRC | KELLER TRUCKING | | | SCAC3 |
| 3021 | KLRE | KELVIN RESOURCE LIMITED | | | SCAC3 |
| 3022 | KLRF | KELLER FARMS | | | SCAC4 |
| 3023 | KLRG | KAHL, ROGER TRUCKING | | | SCAC3 |
| 3024 | KLRH | KLR TRANSPORT INC | | | SCAC3 |
| 3025 | KLRI | KLAMATH RECI INC | | | SCAC3 |
| 3026 | KLRI | K L R TRANSPORT INC | | | SCAC4 |
| 3027 | KLRK | KLEIN TRUCKING INC | | | SCAC3 |
| 3028 | KLRK | K L & T TRUCKING LLC | | | SCAC4 |
| 3029 | KLRP | KLAMATH RIVER TRANSPORTATION INC | | | SCAC3 |
| 3030 | KLRQ | KELLER, JOHN D & SONS | | | SCAC3 |
| 3031 | KLRS | KELLER SPECIALIZED TRANSPORT INC | | | SCAC3 |
| 3032 | KLRS | KELLER FARMS | | | SCAC4 |
| 3033 | KLS | Aerolynx | Callsign: Caracal, | KS | AVCODES |
| 3034 | KLS | Kal Star Aviation, PT. | IATA: KD, Callsign: Kalstar, Ceased operations on 30 November 2017. | RI | AVCODES |
| 3035 | KLS | Kalamazoo, Lake Shore & Chicago Ry. Co. | 8/1920-7/1923 | | NAKINA |
| 3036 | KLS | KALAMAZOO, LAKE SHORE & CHICAGO RAILWAY CO. | | | PWRC |
| 3037 | KLSA | KLS AIR EXPRESS INC | | | SCAC4 |
| 3038 | KLSB | KOLIAS BROS TRUCKING | | | SCAC3 |
| 3039 | KLSC | Kalamazoo, Lake Shore & Chicago Ry. | 1/1994-7/2005 | | NAKINA |
| 3040 | KLSC | Kalamazoo, Lake Shore & Chicago Ry. | 1/94-7/2000 | | NRHS |
| 3041 | KLSC | KALAMAZOO, LAKE SHORE & CHICAGO RAILWAY CO. | | | PWRC |
| 3042 | KLSC | Kalamazoo, Lake Shore and Chicago Railway | | | RSRV |
| 3043 | KLSC | LAKE SHORE & CHICAGO RAILWAY | | | SCAC3 |
| 3044 | KLSE | KELLY, S E | | | SCAC3 |
| 3045 | KLSF | KELSEY FARMS | | | SCAC3 |
| 3046 | KLSF | KALER & SONS LOGISTICS | | | SCAC4 |
| 3047 | KLSH | K & L SHIPPERS INC | | | SCAC4 |
| 3048 | KLSI | KLS TRUCKING INC | | | SCAC4 |
| 3049 | KLSL | KENT LINE SALES LIMITED | | | SCAC4 |
| 3050 | KLSM | KEY LOGISTICS SOLUTIONS LLC (FLATBE | | | SCAC4 |
| 3051 | KLSO | KATZ, L & SONS TRUCKING INC | | | SCAC3 |
| 3052 | KLSO | KELSO E N E | | | SCAC4 |
| 3053 | KLSP | KEYSTONE LIMOUSINE SERVICE INC | | | SCAC3 |
| 3054 | KLSP | KALWAY SPECIALIZED TRANSPORT LTD | | | SCAC4 |
| 3055 | KLSQ | KLIMAS PETROLEUM HAULING | | | SCAC3 |
| 3056 | KLSS | KLS EXPRESS INC | | | SCAC3 |
| 3057 | KLSS | KLASSEN, P CUSTOM FABRICATING | | | SCAC4 |
| 3058 | KLST | KISSIMMEE LOGISTIC SERVICES INC | | | SCAC4 |
| 3059 | KLSV | KING LIMOUSINE SERVICE INC | | | SCAC3 |
| 3060 | KLSV | KENCO TRANSPORTATION | | | SCAC4 |
| 3061 | KLSW | KLASSEN, WALTER FX | | | SCAC4 |
| 3062 | KLSX | Weather Shield MFG, Inc. | added 1/2008 | | NAKINA |
| 3063 | KLSX | Kerford Limestone Co. | added 7/1980; eliminated 10/1984 | | NAKINA |
| 3064 | KLSX | Kerford Limestone Co. | added 7/80; eliminated 10/84 | | NRHS |
| 3065 | KLSX | *KERFORD LIMESTONE CO. | | | PWRC |
| 3066 | KLSX | +WEATHER SHIELD MFG., INC. | | | PWRC |
| 3067 | KLSX | Kerford Limestone | | | RSRV |
| 3068 | KLSX | WEATHER SHIELD MFG., INC. | | | SCAC4 |
| 3069 | KLSY | KELSEY, THOMAS | | | SCAC3 |
| 3070 | KLT | KELLEY TRANSIT COMPANY INC, THE | | | SCAC4 |
| 3071 | KLT | Klingentalbahn | | D | TRAFFIC |
| 3072 | KLT | Kalmar Länstrafik AB | | SE | VKM |
| 3073 | KLTA | KLEIN TRANSPORT | | | SCAC3 |
| 3074 | KLTA | KIELER TRANSPORTATION | | | SCAC4 |
| 3075 | KLTAR | Grupa Azoty “KOLTAR” Sp. z o.o. | | PL | VKM |
| 3076 | KLTB | KLINETOBE, DEAN | | | SCAC3 |
| 3077 | KLTC | KEELE TRUCKING | | | SCAC3 |
| 3078 | KLTC | KERSEY, LAMAR TRUCKING CO INC | | | SCAC4 |
| 3079 | KLTD | K & L TRUCKING | | | SCAC3 |
| 3080 | KLTE | KLINE TRANSIT | | | SCAC3 |
| 3081 | KLTF | KLOKE TRANSFER | | | SCAC3 |
| 3082 | KLTF | KLOKE TRANSFER | | | SCAC4 |
| 3083 | KLTG | K & L TRUCKING INC | | | SCAC3 |
| 3084 | KLTG | K & L TRUCKING INC | | | SCAC4 |
| 3085 | KLTH | KLOTH TRUCK & EQUIPMENT CO | | | SCAC3 |
| 3086 | KLTH | K & L TOOL-MACHINING LTD | | | SCAC4 |
| 3087 | KLTI | KELLEY, C TRUCKING INC | | | SCAC3 |
| 3088 | KLTJ | KILGORE LIVESTOCK TRANSPORTATION LL | | | SCAC4 |
| 3089 | KLTK | KELLY TRUCKING CO | | | SCAC3 |
| 3090 | KLTL | KILBERN TRUCKING AND LEASING INC | | | SCAC3 |
| 3091 | KLTL | KELLY TRANSPORTATION SERVICES LLC | | | SCAC4 |
| 3092 | KLTM | KELLYS TRUCKING INCORPORATED | | | SCAC3 |
| 3093 | KLTO | KALLAM TRANSFER CO | | | SCAC3 |
| 3094 | KLTP | KLT ENTERPRISES | | | SCAC4 |
| 3095 | KLTQ | KELLEY TRUCKING COMPANY | | | SCAC3 |
| 3096 | KLTR | KELLER, THOMAS E TRUCKING INC | | | SCAC3 |
| 3097 | KLTR | KELLER, THOMAS E TRUCKING INC | | | SCAC4 |
| 3098 | KLTS | KOLLMAN LANDSCAPING & TRUCKING SERV | | | SCAC3 |
| 3099 | KLTS | KLT TRANS INC | | | SCAC4 |
| 3100 | KLTT | KELTIC TRANSPORTATION INC | | | SCAC4 |
