| 1 | NN | Air Italy S.p.A. | ICAO: AJR, Callsign: Air Italy, Designator NN recalled by IATA | I | AVCODES |
| 2 | NN | Air Martinique | ICAO: MTQ, Callsign: Air Martinique, Merged in Air Gaudeloupe in July 2000. | MQ | AVCODES |
| 3 | NN | Cardinal Airlines Limited | ICAO: DCF, Callsign: Cardinal Air, Designator NN recalled by IATA | AG | AVCODES |
| 4 | NN | VIM Airlines | ICAO: MOV, Callsign: Mov Air, IATA Prefix: 823, Ceased operations on 16 October 2017. | RUS | AVCODES |
| 5 | NN | China Travel Tours Transportation Services Hong Kong Ltd. (CTTTS) | Bus Service | PRC | AVCODES |
| 6 | NN | Northern Nevada R.R. Corp. | eliminated 7/1998; 7/2000-7/2005 | | NAKINA |
| 7 | NN | Nevada Northern Ry. Co. | 1/1941-10/1966 & 1/1975-1/1980; eliminated 1/1988; added 10/1994 | | NAKINA |
| 8 | NN | Nevada Northern Ry. Co. | 1/52-10/66 & 1/75-1/80; eliminated 1/88; added 10/94 | | NRHS |
| 9 | NN | Northern Nevada R.R. Corp. | eliminated 7/98; 7/2000 | | NRHS |
| 10 | NN | NORTHERN NEVADA RAILROAD CORPORATION [NEVADA NORTHERN RWY.] | | | PWRC |
| 11 | NN | Nevada Northern Railway | | | RSRV |
| 12 | NN | Nevada Northern Railway Co. | | USA | TRAFFIC |
| 13 | NNAC | NEREUS NAVIGATION COMPANY LIMITED | | | SCAC4 |
| 14 | NNAN | NATS NORTH AMERICA'S TRANSPORTATION | | | SCAC4 |
| 15 | NNAP | NORTHERN AIRE TRANSPORT LLC | | | SCAC4 |
| 16 | NNAT | NICK & ANA TRUCKING INC | | | SCAC3 |
| 17 | NNBC | NINE ZERO ZERO SEVEN-THREE ONE ZERO | | | SCAC4 |
| 18 | NNBE | N & B EXPRESS INC | | | SCAC3 |
| 19 | NNCC | NORTHERN CARRIER LLC | | | SCAC4 |
| 20 | NNCE | NANCE TANK LINES | | | SCAC3 |
| 21 | NNCL | NASSAU NAVIGATION CORP LTD | | | SCAC3 |
| 22 | NNCM | NIREUS NAVIGATION COMPANY LIMITED | | | SCAC4 |
| 23 | NNCO | NETTLES & CO INC | | | SCAC3 |
| 24 | NNCP | NATIONAL NAIL CORP | | | SCAC4 |
| 25 | NNCU | CANADIAN ROYALTIES INC | | CDN | BIC |
| 26 | NNCU | Canadian Royalties | | | RSRV |
| 27 | NNDL | NELSON, DARRELL | | | SCAC4 |
| 28 | NNDU | NAVIERA NEPTUNO DEL PERU SA | | | SCAC3 |
| 29 | NNDU | NAVIERA NEPTUNO DEL PERU SA | | | SCAC4 |
| 30 | NNE | NORFOLK SOUTHERN RAILWAY COMPANY [NEW ORLEANS & NORTHEASTERN RR] | | | PWRC |
| 31 | NNEA | NAVEX-NAVIGA | | | SCAC4 |
| 32 | NNEC | NOONAN ENERGY CORP | | | SCAC4 |
| 33 | NNEF | NINE ONE FOUR ZERO-ONE NINE NINE TW | | | SCAC4 |
| 34 | NNFF | NINE ZERO NINE FIVE FIVE FOUR NINE | | | SCAC4 |
| 35 | NNFL | NFL NATIONAL FREIGHT LOGISTICS LLC | | | SCAC4 |
| 36 | NNFN | MPI DRILLING | | | SCAC4 |
| 37 | NNFQ | NINE ZERO ZERO THREE- FOUR SEVEN NI | | | SCAC4 |
| 38 | NNG | Nizhegorodelektrotrans | City: Nizhny Novgorod | RUS | TRAFFIC |
| 39 | NNGL | NEVADA NORTHERN GRAY LINE | | | SCAC3 |
| 40 | NNGS | NORTHERN AG SERVICE INC | | | SCAC4 |
| 41 | NNHQ | NINE ONE THREE ONE-NINE FIVE FIVE E | | | SCAC4 |
| 42 | NNIB | NUBS NIBBLES LLC | | | SCAC4 |
| 43 | NNIL | NII NORTHERN INTERNATIONAL | | | SCAC4 |
| 44 | NNIU | NAUTICA LINE | | | PWRC |
| 45 | NNIU | Nautica Line | | | RSRV |
| 46 | NNIU | NAUTICA LINE | | | SCAC3 |
| 47 | NNIU | NAUTICA LINE | | | SCAC4 |
| 48 | NNKB | Narashino New Keisei Bus | | J | TRAFFIC |
| 49 | NNKG | NIELSEN TRUCKING CO | | | SCAC4 |
| 50 | NNKI | NAVAS TRUCKING INC | | | SCAC4 |
| 51 | NNKL | NELSON TRUCKING LOGISTICS INC | | | SCAC4 |
| 52 | NNLC | NINE - NORTH LOGISTICS INC | | | SCAC4 |
| 53 | NNLG | N & N LOGISTICS INC | | | SCAC4 |
| 54 | NNLI | N & N LEASING INC | | | SCAC3 |
| 55 | NNLI | NEMTAS NEMRUT LIMAN ISLETMELERI A S | | | SCAC4 |
| 56 | NNLL | NAMRON LOGISTICS LLC | | | SCAC4 |
| 57 | NNLU | NIGERIAN NATIONAL SHIPPING LINE | | | SCAC3 |
| 58 | NNME | NELSON, MIKE | | | SCAC4 |
| 59 | NNMH | NORRIS & NORRIS MOBILE HOME | | | SCAC3 |
| 60 | NNMT | N & M TRUCKING INC | | | SCAC3 |
| 61 | NNOE | NINE ONE THREE EIGHT-EIGHT SIX ONE | | | SCAC4 |
| 62 | NNOG | NORTH NATIONAL OUTDOOR GROUP INC | | | SCAC4 |
| 63 | NNPR | NEW YORK & NEW JERSEY PORT RAILROAD CO. | | | PWRC |
| 64 | NNPU | NIGERIAN NATIONAL PETROLEUM CORPORATION | | | PWRC |
| 65 | NNPU | Nigerian National Petroleum Corporation | | | RSRV |
| 66 | NNPU | NIGERIAN NATIONAL PETROLEUM CORP. | | | SCAC3 |
| 67 | NNPW | NIC NAK PATTI WACK | | | SCAC4 |
| 68 | NNQB | NINE ONE FIVE FOUR-EIGHT SIX | | | SCAC4 |
| 69 | NNQC | NINE ONE THREE NINE-FOUR ZERO TWO T | | | SCAC4 |
| 70 | NNRA | NNR AIRCARGO SERVICE (USA INC) | | | SCAC4 |
| 71 | NNRC | NNR GLOBAL LOGISTICS USA INC | | | SCAC4 |
| 72 | NNRX | Nye & Nissen Refrigerator Line Co. (North American Car Corp.) | 7/1935 | | NAKINA |
| 73 | NNRX | NEVADA NORTHERN RAILWAY | | | PWRC |
| 74 | NNSB | NINE ZERO ONE SIX-ONE ONE SIX | | | SCAC4 |
| 75 | NNSL | NORTHERN SERVICE LLC | | | SCAC4 |
| 76 | NNSN | NORTHERN LEASING INC | | | SCAC3 |
| 77 | NNSN | NORTHERN LEASING INC | | | SCAC4 |
| 78 | NNST | N & S TRUCKING INC | | | SCAC3 |
| 79 | NNSX | Newport News Shipbuilding and Dry Dock Co. | 7/1965-1/1994; eliminated 7/1996; added 10/1996; eliminated 1/1997; 7/2000-7/2005 (not listed) | | NAKINA |
| 80 | NNSX | Newport News Shipbuilding and Dry Dock Co. | 7/65-1/94; eliminated 7/96; added 10/96; eliminated 1/97; 7/2000 | | NRHS |
| 81 | NNSX | NEWPORT NEWS SHIPBUILDING & DRY DOCK CO. | | | PWRC |
| 82 | NNSX | Newport News Shipbuilding and Dry Dock | | | RSRV |
| 83 | NNSX | NEWPORT NEWS SHIPBUILDING & DRY DOC | | | SCAC4 |
| 84 | NNTC | NINE ZERO ZERO NINE-THREE NINE FOUR | | | SCAC4 |
| 85 | NNTD | NANETTE DISTRIBUTOR INC | | | SCAC4 |
| 86 | NNTF | NINE ZERO SIX EIGHT NINE TWO FOUR O | | | SCAC4 |
| 87 | NNTI | NATIONAL TRANSPORT INC | | | SCAC3 |
| 88 | NNTI | N & N TRANSPORT INC | | | SCAC4 |
| 89 | NNTK | N & N TRUCKING INC | | | SCAC3 |
| 90 | NNTP | NINETY NINE (99) TRANSPORT INC | | | SCAC4 |
| 91 | NNTR | N & N TRUCKING | | | SCAC4 |
| 92 | NNVC | NATIONAL NAVIGATION CO CAIRO EGYPT | | | SCAC4 |
| 93 | NNVG | Norddeutsche Nahverkehrsgesellschaft mbH | Schenefeld | D | privat-bahn.de |
| 94 | NNVG | NIAGARA NAVIGATION CO | | | SCAC3 |
| 95 | NNW | Nebraska Northwestern Railroad | | | RSRV |
| 96 | NNW | NEBRASKA NORTHWESTERN RAILROAD INC. | | | SCAC4 |
| 97 | NNWT | N & W TRANSFER | | | SCAC3 |
| 98 | NNWT | N N W TRUCKING INC | | | SCAC4 |
| 99 | NNXI | NELSONS TRANSPORT INC | | | SCAC4 |
| 100 | NNXT | NORTENO TRANSPORT | | | SCAC4 |
