| 1 | SQ | Singapore Airlines | ICAO: SIA, Callsign: Singapore, IATA Prefix: 618, Name changed to Singapore Airlines Limited | SGP | AVCODES |
| 2 | SQ | Singapore Airlines Cargo PTE Ltd. | ICAO: SQC, Callsign: Singcargo, IATA Prefix: 618, Merged into Singapore Airlines on 01/04/2018. | SGP | AVCODES |
| 3 | SQ | Norcanair | IATA designator changed to NK | CDN | AVCODES |
| 4 | SQ | Singapore Airlines Limited | ICAO: SIA, Callsign: Singapore, IATA Prefix: 618, Name changed from Singapore Airlines | SGP | AVCODES |
| 5 | SQA | Slovak National Aeroclub | Callsign: Slovak Aeroclub, | SK | AVCODES |
| 6 | SQA | Slovak National Aeroclub | | | ICAO1 |
| 7 | SQAD | SQUARE TRANSPORTATION INC | | | SCAC4 |
| 8 | SQAE | SALLEE INC | | | SCAC4 |
| 9 | SQAG | S T & W BROKERAGE LLC | | | SCAC4 |
| 10 | SQAH | SIMPLY AMISH | | | SCAC4 |
| 11 | SQAL | SOUTHERN LOGISTICS AND EQUIPMENT CO | | | SCAC4 |
| 12 | SQAM | SAMS TRUCKING LLC | | | SCAC4 |
| 13 | SQAN | SEATRANS CHEMICAL TANKERS AS | | | SCAC4 |
| 14 | SQAT | SEVENTH AFRAMAX TANKER CORPORATION | | | SCAC4 |
| 15 | SQAW | SKATES EQUIPMENT | | | SCAC4 |
| 16 | SQAY | SANRITSU LOGISTICS AMERICA INC | | | SCAC4 |
| 17 | SQBR | SOUTH BAY RECYCLING | | | SCAC4 |
| 18 | SQBT | SEASIDES BEST TOUR | | | SCAC4 |
| 19 | SQC | Singapore Airlines Cargo PTE Ltd. | IATA: SQ, Callsign: Singcargo, IATA Prefix: 618, Merged into Singapore Airlines on 01/04/2018. | SGP | AVCODES |
| 20 | SQC | Singapore Airlines Cargo | IATA: SQ | | ICAO1 |
| 21 | SQCA | SOUTHERN CAL TRANSPORT CO | | | SCAC4 |
| 22 | SQCE | SELECT CLASSIC CARRIERS INC | | | SCAC4 |
| 23 | SQCH | SHIPPERS CHOICE TRANSPORTATION LLC | | | SCAC4 |
| 24 | SQCI | SPECIALTY CARRIERS INC | | | SCAC4 |
| 25 | SQCN | STEELCASE CANADA LIMITED | | | SCAC4 |
| 26 | SQCO | STARCO INC | | | SCAC4 |
| 27 | SQCP | SMT COMPANY | | | SCAC4 |
| 28 | SQCQ | SLCS CORPORATION | | | SCAC4 |
| 29 | SQCT | SPECIALTY CONTRACT CARRIERS INC | | | SCAC4 |
| 30 | SQCV | SILVER CREEK EXPRESS INC | | | SCAC4 |
| 31 | SQD | Tomorrow's Aeronautical Museum, Inc. | Callsign: Aero Squad, | USA | AVCODES |
| 32 | SQDL | STORE TO DOOR LLC | | | SCAC4 |
| 33 | SQDN | SUEDEMAS | | | SCAC4 |
| 34 | SQDO | SUNSPACE MODULAR ENCLOSURES INC | | | SCAC4 |
| 35 | SQEC | SPECTRUM CATERING | | | SCAC4 |
| 36 | SQEH | STARLITE ENTERPRISES OF HARDY COUNT | | | SCAC4 |
| 37 | SQEP | SON SHINE EXPRESS | | | SCAC4 |
| 38 | SQES | SCALES EXPRESS INC | | | SCAC4 |
| 39 | SQF | Slovak Air Force | Callsign: Slovak Air Force, | SK | AVCODES |
| 40 | SQF | Slovak Air Force | | | ICAO1 |
| 41 | SQGC | SPICER PLUS INC | | | SCAC4 |
| 42 | SQGS | SITTON LOGISTICS LLC | | | SCAC4 |
| 43 | SQH | Ford Aire | Callsign: Susquehanna, | USA | AVCODES |
| 44 | SQH | Alaska Juneau Aeronautics, Inc. | Callsign: Sasquatch, Name changed to Seaport Airlines, Inc. | USA | AVCODES |
| 45 | SQH | Seaport Airlines, Inc. | IATA: K5, Callsign: Sasquatch, Ceased operations on 20 September 2016 and filed for Chapter 7 bankruptcy. Name changed from Alaska Juneau Aeronautics, Inc. | USA | AVCODES |
| 46 | SQHC | STROHL OIL CO | | | SCAC4 |
| 47 | SQHD | SAHIR TRUCKING LTD | | | SCAC4 |
| 48 | SQHE | SANDY HILLS ELK RANCH | | | SCAC4 |
| 49 | SQHG | SEA CENTRAL SHIPPING CORPORATION | | | SCAC4 |
| 50 | SQHI | STAHL OIL COMPANY INC | | | SCAC4 |
| 51 | SQHK | SMITH, CURTIS TRUCKING | | | SCAC4 |
| 52 | SQHM | SCHMUCKAL OIL CO | | | SCAC4 |
| 53 | SQHN | SCHREINERS INC | | | SCAC4 |
| 54 | SQHO | SHORES OIL COMPANY | | | SCAC4 |
| 55 | SQIG | SUNSET LOGISTICS INC | | | SCAC4 |
| 56 | SQIH | SHINE TRANSPORTATION INC | | | SCAC4 |
| 57 | SQIN | SUMMIT TRANSPORTATION | | | SCAC4 |
| 58 | SQIY | SALT CITY INC | | | SCAC4 |
| 59 | SQKD | SOUTHEAST CONSOLIDATORS INC (LOGIST | | | SCAC4 |
| 60 | SQKI | SEAQUA TRUCKING INC | | | SCAC4 |
| 61 | SQKO | SOUTHEAST CONSOLIDATORS INC (BROKER | | | SCAC4 |
| 62 | SQKR | SHELDRAKE TRANSPORT INC | | | SCAC4 |
| 63 | SQKT | SOUTHLAKE TRANSPORT INC | | | SCAC4 |
| 64 | SQKY | SKY TRANSPORT INC | | | SCAC4 |
| 65 | SQL | Servicios de Alouiler Aereo, S.A. de C.V. | Callsign: Alquiler, | MEX | AVCODES |
| 66 | SQL | Servicos De Alquiler | | | ICAO1 |
| 67 | SQLA | SALAAMA TRUCKING INC | | | SCAC4 |
| 68 | SQLB | STONERIDGE QUARRIES LTD | | | SCAC4 |
| 69 | SQLC | STRUCTURAL TECH CORPORATION LTD | | | SCAC4 |
| 70 | SQLD | SPECIAL LOGISTICS INC | | | SCAC4 |
| 71 | SQLF | STARLITE COLONY FARMS LTD | | | SCAC4 |
| 72 | SQLJ | SAN QUINTIN LOGISTICS | | | SCAC4 |
| 73 | SQLL | SQL | | | SCAC4 |
| 74 | SQLO | SPECTRUM LOGISTICS | | | SCAC4 |
| 75 | SQLR | SEALE MARINE | | | SCAC4 |
| 76 | SQLV | SLIM LINE VENDING INTERNATIONAL LTD | | | SCAC4 |
| 77 | SQM | Evergreen Express Airways | Callsign: Skwim, | USA | AVCODES |
| 78 | SQM | Siam Air Transport Co., Ltd. | IATA: O8, Callsign: Golden Fin, IATA Prefix: 874, | T | AVCODES |
| 79 | SQM | Sociedad Química y Minera | | RCH | TRAFFIC |
| 80 | SQMA | SMITH, ARTHUR TRUCKING INC | | | SCAC4 |
| 81 | SQMC | S & M TRANSPORT | | | SCAC4 |
| 82 | SQMD | SIERRA MOUNTAIN INC | | | SCAC4 |
| 83 | SQME | SCOTT PETROLEUM CORPORATION | | | SCAC4 |
| 84 | SQMI | STRUCTURAL METALS INC | | | SCAC4 |
| 85 | SQMM | SCRUMMASTER | | | SCAC4 |
| 86 | SQMN | S M TRANSPORT | | | SCAC4 |
| 87 | SQMS | SUPERIOR MARITIME SERVICES INC | | | SCAC4 |
| 88 | SQMV | SIMMONS MOVING & STORAGE INC | | | SCAC4 |
| 89 | SQNA | SBS TRANSPORTATION INC | | | SCAC4 |
| 90 | SQNC | SONOCO LIMITED | | | SCAC4 |
| 91 | SQND | SENIOR OIL INC | | | SCAC4 |
| 92 | SQNE | SEQUOIALINE INC | | | SCAC4 |
| 93 | SQNI | SHANE TRANSPORTATION INC | | | SCAC4 |
| 94 | SQNP | SUN TRANSPORT | | | SCAC4 |
| 95 | SQNQ | SHELLHORN & HILL INC | | | SCAC4 |
| 96 | SQNS | SUNSTATE CARRIERS INC | | | SCAC4 |
| 97 | SQNT | STONES TRANSPORT INC | | | SCAC4 |
| 98 | SQOC | SOCI PETROLEUM INC | | | SCAC4 |
| 99 | SQOI | SCITUATE OIL CO INC | | | SCAC4 |
| 100 | SQOL | STAR OIL CO | | | SCAC4 |
