| 1 | PO | Polar Air Cargo, Inc. | ICAO: PAC, Callsign: Polar, IATA Prefix: 403, Name changed to Polar Air Cargo Worldwide, Inc. ICAO Callsign changed from Polar Tiger | USA | AVCODES |
| 2 | PO | Protea Lugdiens (EDMS.) BPK | Callsign: Protea, | ZA | AVCODES |
| 3 | PO | Polar Air Cargo, Inc. | ICAO: PAC, Callsign: Polar Tiger, IATA Prefix: 403, ICAO Callsign changed to Polar | USA | AVCODES |
| 4 | PO | Aeropelican Air Services Pty Ltd. | ICAO: PEL, Designator PO recalled by IATA. Established on 23 October 1968 and started operations on 1 July 1971. | AUS | AVCODES |
| 5 | PO | Polar Air Cargo Worldwide, Inc. | ICAO: PAC, Callsign: Polar, IATA Prefix: 403, Name changed from Polar Air Cargo, Inc. ICAO Callsign changed from Polar Tiger | USA | AVCODES |
| 6 | PO | Compagnie du chemin de fer Paris et Orléans | | F | TRAFFIC |
| 7 | POA | Portuguese Army | Callsign: Portuguese Army, | P | AVCODES |
| 8 | POA | Portuguese Army | | | ICAO1 |
| 9 | POAA | POLAR TRANSPORT | | | SCAC4 |
| 10 | POAB | PROFILES AB | | | SCAC3 |
| 11 | POAC | POOLE AIR COURIERS | | | SCAC3 |
| 12 | POAC | POIRIER, SERGE | | | SCAC4 |
| 13 | POAD | POOLE, A D TRANSPORTATION CO INC | | | SCAC3 |
| 14 | POAE | POL-TRAILER CORP | | | SCAC4 |
| 15 | POAF | PORTLAND AIR FREIGHT INC | | | SCAC3 |
| 16 | POAF | PORTLAND AIR FREIGHT INC | | | SCAC4 |
| 17 | POAG | PRO AG TRANSPORT INC | | | SCAC3 |
| 18 | POAJ | PROA INTERNACIONAL Y LOGISTICA SA D | | | SCAC4 |
| 19 | POAK | Port of Oakland Ry. | 1/1980-7/2005 | | NAKINA |
| 20 | POAK | Port of Oakland Ry. | 1/80-7/2000 | | NRHS |
| 21 | POAK | PORT OF OAKLAND RAILWAY | | | PWRC |
| 22 | POAK | Port of Oakland Railway | | | RSRV |
| 23 | POAK | PORT OF OAKLAND RAILWAY | | | SCAC3 |
| 24 | POAK | POLLARD TRUCKING INC | | | SCAC4 |
| 25 | POAN | POLREY FURNITURE INC | | | SCAC4 |
| 26 | POAP | PORTLAND AIRPORT LIMOUSINE COMPANY | | | SCAC3 |
| 27 | POAQ | PONTIAC CARTAGE CO INC | | | SCAC3 |
| 28 | POAQ | POTTER CHRISTMAS TREE FARM | | | SCAC4 |
| 29 | POAR | PRO-AIRE TRANSPORT INC | | | SCAC3 |
| 30 | POAR | PABCO INC | | | SCAC4 |
| 31 | POAS | POST & SONS TRANSFER CO | | | SCAC3 |
| 32 | POAS | POLYTECH NETTING INDUSTRIES DE MEXI | | | SCAC4 |
| 33 | POAT | PORTERS AUTO TRANSPORT, INC | | | SCAC3 |
| 34 | POAU | PRIMY OCEAN AIR LOGISTICS CO LTD | | PRC | BIC |
| 35 | POB | Servicios Aereos Poblanos, S.A. de C.V. | Callsign: Poblanos, | MEX | AVCODES |
| 36 | POB | Servicios Aereos Poblanos | | | ICAO1 |
| 37 | POBC | P&O BULK CARRIERS LTD | | | SCAC3 |
| 38 | POBC | P&O BULK CARRIERS LTD | | | SCAC4 |
| 39 | POBE | POLAR BEAR EXPRESS INC | | | SCAC3 |
| 40 | POBE | POULIN, MARIE-LOUIS | | | SCAC4 |
| 41 | POBF | PORTER BROS FERTILIZER | | | SCAC3 |
| 42 | POBI | PORT BIENVILLE RAILROAD | | | PWRC |
| 43 | POBI | P O BOX INTERNATIONAL/U S A | | | SCAC4 |
| 44 | POBK | PHILADELPHIA COCA-COLA BOTTLING COM | | | SCAC4 |
| 45 | POBL | PERRYOPOLIS BUS LINES | | | SCAC3 |
| 46 | POBL | PORT LINDEN CORPORATION | | | SCAC4 |
| 47 | POBO | POOR BOY MOVERS INC | | | SCAC3 |
| 48 | POBQ | POTTER, BEN FELTON | | | SCAC3 |
| 49 | POBQ | PROFICIENT MACHINING INC | | | SCAC4 |
| 50 | POBR | PORT OF ROYAL SLOPE RAILROAD | | | PWRC |
| 51 | POBR | POOL BROTHERS | | | SCAC3 |
| 52 | POBR | PROSSER, JOHN CHARLES | | | SCAC4 |
| 53 | POBS | POLYBOIS INC | | | SCAC4 |
| 54 | POBT | POOL, RICHARD J | | | SCAC4 |
| 55 | POBU | PAN OCEAN SHIPPING CO LTD | | | SCAC3 |
| 56 | POBU | STX PAN OCEAN CO LTD | | | SCAC4 |
| 57 | POBY | POOLS BY ANGELO | | | SCAC4 |
| 58 | POC | Pocono Air Lines, Inc. | Callsign: Pocono, | USA | AVCODES |
| 59 | POC | Pocono Air Lines | | | ICAO1 |
| 60 | POC | P&O Cruises | | | TRAFFIC |
| 61 | POCA | PORT OF CATOOSA TERMINAL RAILROAD (FORMERLY PORT OF CATOOSA) | | | PWRC |
| 62 | POCB | POCO ENTERPRISES INC | | | SCAC3 |
| 63 | POCB | PREMIER FOODS INC | | | SCAC4 |
| 64 | POCC | PORT CITY CAB CO | | | SCAC3 |
| 65 | POCC | PHILLIPS OIL COMPANY INC | | | SCAC4 |
| 66 | POCD | PORT OF CASCADE LOCKS | | | SCAC3 |
| 67 | POCE | PONCA CITY EXPRESS INC | | | SCAC3 |
| 68 | POCE | PRODUCERS TRANSPORT | | | SCAC4 |
| 69 | POCF | P & O CONTAINERS LTD | | | SCAC3 |
| 70 | POCG | PORT CITY TRUCKING INC | | | SCAC3 |
| 71 | POCH | POCH, CHARLES INC | | | SCAC3 |
| 72 | POCH | POTTS TRANSPORT CO INC | | | SCAC4 |
| 73 | POCI | PORT CARGO MOTOR LINES INC | | | SCAC3 |
| 74 | POCJ | POTEAT, CHARLES J | | | SCAC3 |
| 75 | POCK | POLLOCK TRANSPORT INC | | | SCAC3 |
| 76 | POCL | P&O NEDLLOYD CONTAINER LINES | | | SCAC3 |
| 77 | POCL | P & O LINES | | | SCAC4 |
| 78 | POCM | PORT CITY TRANSPORTATION | | | SCAC3 |
| 79 | POCMT | Pocono Mountain Trails | | USA | TRAFFIC |
| 80 | POCN | PETRO CHEMICAL TRANSPORT INC | | | SCAC3 |
| 81 | POCN | PETRO CHEMICAL TRANSPORT | | | SCAC4 |
| 82 | POCO | PARTON OIL CO INC | | | SCAC3 |
| 83 | POCP | PORTLAND CORP | | | SCAC3 |
| 84 | POCQ | PONTIAC CARTAGE INC | | | SCAC3 |
| 85 | POCQ | PORTERS CASH FUEL | | | SCAC4 |
| 86 | POCR | PAR LOGISTICS INC | | | SCAC4 |
| 87 | POCS | POTISEK, MARIO ALBERTO | | | SCAC4 |
| 88 | POCT | POCONO COAST TRANSPORTATION INC | | | SCAC4 |
| 89 | POCU | MAERSK A/S | | DK | BIC |
| 90 | POCU | P & O CONTAINERS, LT. | | | SCAC3 |
| 91 | POCU | P & O NEDLLOYD BV | | | SCAC4 |
| 92 | POCW | PRUETT OIL CO INC | | | SCAC4 |
| 93 | POCX | Pierce Oil Corp. (Pierce Petroleum Corp.) | 7/1930 | | NAKINA |
| 94 | POCX | Pierce Oil Corp. | 8/1920-7/1923 | | NAKINA |
| 95 | POCX | PIERCE PETROLEUM CORP. [PIERCE OIL CORP.] | | | PWRC |
| 96 | POCY | PORT CITY EXPRESS | | | SCAC3 |
| 97 | POCY | PACKO, TONY FOOD COMPANY | | | SCAC4 |
| 98 | POCZ | POTASH CORP. | | | PWRC |
| 99 | POD | PACT Proair Charter Transport GmbH | Callsign: Freightdogs, | D | AVCODES |
| 100 | PODA | POSSIDENTO, D A INC | | | SCAC3 |
