| 601 | QOTX | QO Chemicals, Inc. | added 10/84; 1/94; eliminated 10/95 | | NRHS |
| 602 | QOTX | Great Lakes Chemical Corp., Specialty Chemicals | added 10/95; 7/2000 | | NRHS |
| 603 | QOTX | *QUAKER OATS COMPANY, CHEMICALS DIV. (QO CHEMICALS, INC.) | | | PWRC |
| 604 | QOTX | +GREAT LAKES CHEMICAL CORPORATION, SPECIALTY CHEMICALS | | | PWRC |
| 605 | QOTX | Quaker Oats Chemicals Division | | | RSRV |
| 606 | QOTX | QO CHEMICALS, INC. | | | SCAC4 |
| 607 | QOVX | Quaker Oil & Tank Co. | 7/1923 | | NAKINA |
| 608 | QOVX | QUAKER OIL & TANK CO. | | | PWRC |
| 609 | QP | Airkenya Aviation Ltd. d/b/a Regional Air | IATA Prefix: 853, Name changed to Airkenya Express Ltd. Formerly Airkenya Aviation Ltd. | EAK | AVCODES |
| 610 | QP | Caspair Ltd. | ICAO: SAL, Callsign: Sunbird, Ceased operations. Designator QP recalled by IATA | EAK | AVCODES |
| 611 | QP | Caspair Ltd. | Callsign: Caspair, | EAK | AVCODES |
| 612 | QP | Airkenya Express Ltd. | ICAO: XAK, IATA Prefix: 853, Name changed from Airkenya Aviation Ltd. d/b/a Regional Air. Formerly Airkenya Aviation Ltd. | EAK | AVCODES |
| 613 | QP | SNV Aviation Pvt Ltd t/a Akasa Air | ICAO: AKJ, Callsign: Akasa Air, | IND | AVCODES |
| 614 | QPAC | QUEST PARTNERS COMPANY | | | SCAC3 |
| 615 | QPCU | QUIMPAC DE COLOMBIA | | CO | BIC |
| 616 | QPCU | QUIMPAC DE COLOMBIA | | | SCAC4 |
| 617 | QPCX | General Electric Rail Services Corp. | 7/2000-7/2005 | | NAKINA |
| 618 | QPCX | General Electric Railcar Services Corp. | 1/1994 | | NAKINA |
| 619 | QPCX | The Quaker Petroleum Co. | 7/1930-4/1947 | | NAKINA |
| 620 | QPCX | The Quaker Petroleum Co. | Apr-38 | | NRHS |
| 621 | QPCX | General Electric Railcar Services Corp. | Jan-94 | | NRHS |
| 622 | QPCX | General Electric Rail Services Corp. | Jul-00 | | NRHS |
| 623 | QPCX | *QUAKER PETROLEUM CO. | | | PWRC |
| 624 | QPCX | +GENERAL ELECTRIC RAILCAR SERVICES CORP | | | PWRC |
| 625 | QPCX | General Electric Rail Services Corporation | | | RSRV |
| 626 | QPFI | QUALITY PAPER FIBERS INC | | | SCAC3 |
| 627 | QPIS | QUALITY PALLETS INC | | | SCAC4 |
| 628 | QPKD | QUICK-PAK DELIVERY SERVICE | | | SCAC3 |
| 629 | QPKD | QUICK PICK DELIVERY | | | SCAC4 |
| 630 | QPL | Grupo Desarrollador Qpula | Callsign: Qupula, | MEX | AVCODES |
| 631 | QPLL | QUAIL, PAUL | | | SCAC4 |
| 632 | QPLS | QP-LS LLC | | | SCAC4 |
| 633 | QPML | QUINTERO PACHECO, MARIA LAURA | | | SCAC4 |
| 634 | QPMT | QUANTUM PREMIUM TRANSPORT (A DIVISI | | | SCAC3 |
| 635 | QPMT | QUANTUM PREMIUM TRANSPORT (A DIVISI | | | SCAC4 |
| 636 | QPPD | QUALITY PETROLEUM PRODUCTS INC | | | SCAC4 |
| 637 | QPPG | QUALITREE PROPAGATORS INC | | | SCAC4 |
| 638 | QPPL | QUILLS PICTURE PERFECT LIMOUSINE SE | | | SCAC3 |
| 639 | QPSF | QUALY-PAK SPECIALTY FOODS INC | | | SCAC3 |
| 640 | QPTC | QUEENS PRODUCT TANKER CORPORATION | | | SCAC4 |
| 641 | QPTP | Q P TRANSPORTATION INC | | | SCAC3 |
| 642 | QPXP | QUIK PICK EXPRESS LLC | | | SCAC4 |
| 643 | QPZC | QUINLAN PRETZEL COMPANY | | | SCAC3 |
| 644 | QQ | Alliance Airlines PTY Limited | ICAO: FWQ, ICAO designator changed to QQA. Name changed from Flight West Airlines Pty Ltd. Designator YC recalled by IATA | AUS | AVCODES |
| 645 | QQ | Reno Air, Inc. | ICAO: ROA, Callsign: Reno Air, Merged in American Airlines | USA | AVCODES |
| 646 | QQ | Flight West Airlines Pty Ltd. | ICAO: FWQ, Name changed to Alliance Airlines PTY Limited. Designator YC recalled by IATA | AUS | AVCODES |
| 647 | QQ | Aerovias Quisqueyana Ltda. | Callsign: Quisqueyana, | DOM | AVCODES |
| 648 | QQ | Alliance Airlines PTY Limited | ICAO: QQA, Callsign: Alli, ICAO designator changed to UTY. ICAO designator changed from FWQ | AUS | AVCODES |
| 649 | QQ | Alliance Airlines PTY Limited | ICAO: UTY, Callsign: Alli, ICAO designator changed from QQA. ICAO designator changed from FWQ | AUS | AVCODES |
| 650 | QQA | Alliance Airlines PTY Limited | IATA: QQ, Callsign: Alli, ICAO designator changed to UTY. ICAO designator changed from FWQ | AUS | AVCODES |
| 651 | QQE | Qatar Executive | | Q | AVCODES |
| 652 | QQIU | QINGDAO WSR CONTAINER SERVICE CO., LTD | | PRC | BIC |
| 653 | QQLI | QUIS QUEYA LINES INC MIAMI FL | | | SCAC3 |
| 654 | QR | Qatar Airways (W.L.L.) | ICAO: QTR, Callsign: Qatari, IATA Prefix: 157, Name changed to Qatar Airways Group Q.C.S.C. | Q | AVCODES |
| 655 | QR | Air Satellite, Inc. | ICAO: ASJ, Callsign: Satellite, Designator HV recalled by IATA | CDN | AVCODES |
| 656 | QR | Centrafrique | | RCA | AVCODES |
| 657 | QR | Qatar Airways Group Q.C.S.C. | ICAO: QTR, Callsign: Qatari, IATA Prefix: 157, Name changed from Qatar Airways (W.L.L.) | Q | AVCODES |
| 658 | QR | Queensland Rail | | AUS | TRAFFIC |
| 659 | QRAC | QUARRY RIDGE ASPHALT | | | SCAC4 |
| 660 | QRBQ | QUIRK BROS MOTOR SERVICE | | | SCAC3 |
| 661 | QRBQ | QKR LLC | | | SCAC4 |
| 662 | QRC | Quebec Ry. Corp. Inc. | 7/2000-7/2005 | | NAKINA |
| 663 | QRC | Quebec Ry. Corp. Inc. | Jul-00 | | NRHS |
| 664 | QRC | QUEBEC RAILWAY CORP. | | | PWRC |
| 665 | QRC | Quebec Railway Corporation | | | RSRV |
| 666 | QRC | QUEBEC RAILWAY CORPORATION INC | | | SCAC4 |
| 667 | QREX | General American Transportation Corp. | 7/1937 | | NAKINA |
| 668 | QREX | Quaker City Refrigerator Line (General American Tank Car Corp.) | 7/1935 | | NAKINA |
| 669 | QREX | Quaker City Refrigerator Line | 7/1930-7/1932 | | NAKINA |
| 670 | QREX | QUAKER CITY REFRIGERATOR LINE (GENERAL AMERICAN TRANSPORTATION CORP.) | | | PWRC |
| 671 | QRKQ | QUIRK MOVING & STORAGE | | | SCAC3 |
| 672 | QRKQ | QUARTERBACK TRANSPORTATION INC | | | SCAC4 |
| 673 | QRKT | QUARTERBACK TRANSPORTATION USA INC | | | SCAC4 |
| 674 | QRLS | QUARLES PETROLEUM INC | | | SCAC4 |
| 675 | QRMA | QUIROGA RODRIGUEZ, MARIO ALBERTO | | | SCAC4 |
| 676 | QRMC | QUALITY READY MIX CONCRETE CO | | | SCAC3 |
| 677 | QRMT | Q R M TRANSPORTATION INC | | | SCAC3 |
| 678 | QRN | QR National | Formerly Queensland Rail and Interail | AUS | TRAFFIC |
| 679 | QROG | QIROGA TRANSPORT LLC | | | SCAC4 |
| 680 | QRON | QUINLAN, RON | | | SCAC4 |
| 681 | QRPI | QUALITY REPAIR INC | | | SCAC4 |
| 682 | QRR | Quincy R.R. Co. | 1/1975-7/2005 | | NAKINA |
| 683 | QRR | Quincy R.R. Co. | 1/75-7/2000 | | NRHS |
| 684 | QRR | QUINCY RAILROAD COMPANY | | | PWRC |
| 685 | QRR | Quincy Railroad | | | RSRV |
| 686 | QRRU | Q1 INTERMODAL | | | SCAC3 |
| 687 | QRRU | Q ONE (1) INTERMODAL | | | SCAC4 |
| 688 | QRSM | QRS | | | SCAC4 |
| 689 | QRSX | Quality Railway Services & Supply Co. | 7/2000; eliminated 7/2001; added 10/2001; 7/2005; eliminated 4/2007 | | NAKINA |
| 690 | QRSX | Quality Railway Services & Supply Co. | 7/2000; eliminated 7/2001 | | NRHS |
| 691 | QRSX | QUALITY RAILWAY SERVICES & SUPPLY COMPANY | | | PWRC |
| 692 | QRSX | Quality Railway Services and Supply | | | RSRV |
| 693 | QRSX | QUALITY RAILWAY SERVICES & SUPPLY C | | | SCAC4 |
| 694 | QRT | 4D Air Co. Ltd. | Callsign: Quartet, | T | AVCODES |
| 695 | QRT | 4D Air | | | ICAO1 |
| 696 | QRTC | QUICK RESPONSE TRUCKING CO | | | SCAC3 |
| 697 | QRTC | QUIROGA TRANSFER LLC | | | SCAC4 |
| 698 | QRTT | QUASAR TRANSPORT | | | SCAC3 |
| 699 | QRWS | QUICK ROADWAY SERVICES | | | SCAC4 |
| 700 | QS | Travel Service, a.s. | ICAO: TVS, Callsign: Skytravel, Name changed to Smartwings, a.s. w.e.f. 10 December 2018. Designator QS reinstated by IATA | CZ | AVCODES |
