| 3501 | WPCX | Transportation Management, Inc. | 1/1975; added 4/1975; eliminated 7/1976 | | NAKINA |
| 3502 | WPCX | Missouri Valley Walnut Co. | added 7/1976; 1/1980; eliminated 1/1982 | | NAKINA |
| 3503 | WPCX | Transportation Management, Inc. | 1/75; added 4/75 | | NRHS |
| 3504 | WPCX | Missouri Valley Walnut Co. | 1/80; eliminated 1/82 | | NRHS |
| 3505 | WPCX | MISSOURI VALLEY WALNUT CO. (TRANSPORTATION MANAGEMENT, INC.) | | | PWRC |
| 3506 | WPCY | WILLOW PUBLISHING COMPANY | | | SCAC4 |
| 3507 | WPDI | W P D INC | | | SCAC4 |
| 3508 | WPDQ | WOLVERINE PRODUCE INC | | | SCAC4 |
| 3509 | WPDR | WEST PENN DIESEL AND | | | SCAC4 |
| 3510 | WPE | WEST PITTSON-EXETER RAILROAD CO. | | | PWRC |
| 3511 | WPEH | WALTON, PHIL ENTERPRISES HAULING LT | | | SCAC4 |
| 3512 | WPEK | WESPAK FISHERIES LTD | | | SCAC4 |
| 3513 | WPEL | WESTERN PACIFIC EXPRESS LLC | | | SCAC4 |
| 3514 | WPEN | WPE TRANSPORT LLC | | | SCAC4 |
| 3515 | WPES | WEST POINT ENTERPRISES | | | SCAC4 |
| 3516 | WPET | WESTERN PETROLEUM INC | | | SCAC4 |
| 3517 | WPEX | Wabash Power Equipment Co. | added 7/1990; 1/1994-7/2005; eliminated 10/2008 | | NAKINA |
| 3518 | WPEX | Wabash Power Equipment Co. | added 7/90; 1/94-7/2000 | | NRHS |
| 3519 | WPEX | WABASH POWER EQUIPMENT COMPANY | | | PWRC |
| 3520 | WPEX | Wabash Power Equipment | | | RSRV |
| 3521 | WPEX | WABASH POWER EQUIPMENT COMPANY | | | SCAC4 |
| 3522 | WPGX | Western Paving Construction Co. | added 4/1974; 1/1975-1/1980; eliminated 1/1980; 1/1994-7/2005 (not listed) | | NAKINA |
| 3523 | WPGX | Western Paving Construction Co. | added 4/74; 1/75-7/2000 | | NRHS |
| 3524 | WPGX | WESTERN PAVING CONSTRUCTION CO. | | | PWRC |
| 3525 | WPGX | Western Paving Construction | | | RSRV |
| 3526 | WPGX | WESTERN PAVING CONSTRUCTION CO | | | SCAC4 |
| 3527 | WPH | Wat Phnom Airlines | IATA: WD, Callsign: Wat Phnom, IATA Prefix: 913, Ceased operations during 2014. | K | AVCODES |
| 3528 | WPHX | Waite Phillips Co. | 7/1923 | | NAKINA |
| 3529 | WPHX | Wacker Polymers, LP | added 10/2008 | | NAKINA |
| 3530 | WPHX | *WAITE PHILLIPS CO. | | | PWRC |
| 3531 | WPHX | +WACKER POLYMERS, LP | | | PWRC |
| 3532 | WPHX | WACKER POLYMERS LP | | | SCAC4 |
| 3533 | WPIL | WPI LOGISTICS LLC | | | SCAC4 |
| 3534 | WPIM | WALLER PETROLEUM INC | | | SCAC4 |
| 3535 | WPIQ | WESTERN PRIDE INC | | | SCAC4 |
| 3536 | WPIX | WHOLESALE POWER, INC. | | | PWRC |
| 3537 | WPIX | WHOLESALE POWER INC | | | SCAC4 |
| 3538 | WPIZ | WALPORT INC. | | | PWRC |
| 3539 | WPK | Air-Lift Associates, Inc. | Callsign: Wolfpack, | USA | AVCODES |
| 3540 | WPK | Air-Lift Associates | | | ICAO1 |
| 3541 | WPK | | Real: KZK GOP, City: Katowice | PL | TRAFFIC |
| 3542 | WPKGSG | WPK Gdansk-Sopot-Gdynia | | PL | TRAFFIC |
| 3543 | WPKL | WILHEIT PACKAGING LLC | | | SCAC4 |
| 3544 | WPKSLU | Wojewódzkie Przedsiębiorstwo Komunikacyjne w Słupsku | City: Słupsk | PL | TRAFFIC |
| 3545 | WPKT | WOLF PAK TRANSPORT LLC | | | SCAC4 |
| 3546 | WPL | Aeronaves del Peru S.A. | Callsign: Peru, | PE | AVCODES |
| 3547 | WPLN | WORLD PACIFIC LINE | | | SCAC4 |
| 3548 | WPLT | WIRCO PRODUCTS LIMITED | | | SCAC4 |
| 3549 | WPLX | White Provision Co., Inc. | 7/1932-7/1935 | | NAKINA |
| 3550 | WPLX | North American Car Corp. | added 1/1967; 4/1970-1/1980; eliminated 1/1984 | | NAKINA |
| 3551 | WPLX | General Electric Railcar Services Corp. | added 1/1984; 1/1994; eliminated 10/1994 | | NAKINA |
| 3552 | WPLX | North American Car Corp. | added 1/67; 4/70-1/80 | | NRHS |
| 3553 | WPLX | General Electric Railcar Services Corp. | 1/94; eliminated 10/94 | | NRHS |
| 3554 | WPLX | WHITE PROVISION CO., INC. | | | PWRC |
| 3555 | WPLX | (NATX) GENERAL ELECTRIC RAILCAR SERVICES CORPORATION | | | PWRC |
| 3556 | WPLX | White Provision Co. (GE Rail Services) | | | RSRV |
| 3557 | WPMC | WESTERN POLYMER CORP | | | SCAC4 |
| 3558 | WPMI | WILLIS PERMIAN MOVERS INC | | | SCAC4 |
| 3559 | WPMU | UNION PACIFIC RAILROAD COMPANY | | | PWRC |
| 3560 | WPMU | Western Pacific Railroad (Union Pacific Railroad) | | | RSRV |
| 3561 | WPMW | Western Pacific R.R. Co. | added 1/1984; eliminated 10/1987 | | NAKINA |
| 3562 | WPMW | Union Pacific R.R. Co. | added 10/1987; 1/1994-7/2005 | | NAKINA |
| 3563 | WPMW | Western Pacific R.R. Co. | eliminated 10/87 | | NRHS |
| 3564 | WPMW | Union Pacific R.R. Co. | added 10/87; 1/94-7/2000 | | NRHS |
| 3565 | WPMW | UNION PACIFIC RAILROAD CO. [WESTERN PACIFIC RR.] (MAINTENANCE OF WAY EQUIPMENT) | | | PWRC |
| 3566 | WPMW | Western Pacific Railroad (Union Pacific Railroad) | | | RSRV |
| 3567 | WPMW | WINNIPEG PATTERN & MODEL WORKS LTD | | | SCAC4 |
| 3568 | WPNT | WALKERS POINT MARINA | | | SCAC4 |
| 3569 | WPNX | Wilson Provision Co. (North American Car Corp.) | 7/1932-7/1935 | | NAKINA |
| 3570 | WPNX | WILSON PROVISION CO. (NORTH AMERICAN CAR CORP.) | | | PWRC |
| 3571 | WPOM | WPO MANAGEMENT LIMITED | | | SCAC4 |
| 3572 | WPOS | WASHINGTON MOVERS INC | | | SCAC4 |
| 3573 | WPPI | WOODMONT PETROLEUM PRODUCTS INC | | | SCAC4 |
| 3574 | WPPL | WESTPORT PETROLEUM INC | | | SCAC4 |
| 3575 | WPPN | WEST PLAINS PROPANE INC | | | SCAC4 |
| 3576 | WPPP | WESTERN PACIFIC PULP AND PAPER | | | SCAC4 |
| 3577 | WPPT | WESTPOINT STEVENS, INC | | | SCAC1 |
| 3578 | WPPV | White Plains & Pleasantville Bus Lines | | US-NY | TRAFFIC |
| 3579 | WPPX | West Penn Power Co. | 8/1920-7/1930 | | NAKINA |
| 3580 | WPPX | WestPoint Pepperell, Inc. | added 1/1978; 1/1980; eliminated 4/1982 | | NAKINA |
| 3581 | WPPX | WestPoint Pepperell, Inc. | added 1/78; 1/80; eliminated 4/82 | | NRHS |
| 3582 | WPPX | *WEST PENN POWER CO. | | | PWRC |
| 3583 | WPPX | *WESTPOINT PEPPERELL, INC. | | | PWRC |
| 3584 | WPR | Auckland Regional Rescue Helicopter Trust | Callsign: Westpac Rescue, | NZ | AVCODES |
| 3585 | WPR | Auckland Regional Rescue Helicopter Trust | | | ICAO1 |
| 3586 | WPRB | Western Pacific R.R. Co. | 7/1965-4/1970 | | NAKINA |
| 3587 | WPRB | Western Pacific R.R. Co. | 7/65-4/70 | | NRHS |
| 3588 | WPRB | WESTERN PACIFIC RAILROAD CO. | | | PWRC |
| 3589 | WPRC | WELL PORT CONTAINER LINE INC | | | SCAC4 |
| 3590 | WPRD | WOODWELL PRODUCTS | | | SCAC4 |
| 3591 | WPRP | W P RAULS | | | SCAC4 |
| 3592 | WPRR | Willamette & Pacific R.R., Inc. | added 7/1993; 1/1994-7/2005 | | NAKINA |
| 3593 | WPRR | Willamette & Pacific R.R., Inc. | added 7/93; 1/94-7/2000 | | NRHS |
| 3594 | WPRR | WILLAMETTE & PACIFIC RAILROAD COMPANY, INC. | | | PWRC |
| 3595 | WPRR | Willamette and Pacific Railroad | | | RSRV |
| 3596 | WPRR | WILLAMETTE & PACIFIC RAILROAD INC | | | SCAC4 |
| 3597 | WPRR | Willamette & Pacific | | USA | TRAFFIC |
| 3598 | WPRU | WATERMAN OF PUERTO RICO-USA INC | | | PWRC |
| 3599 | WPRU | Waterman of Puerto Rico-USA | | | RSRV |
| 3600 | WPRX | Wainwright Producers and Refiners Ltd. | added 4/1956; 10/1957-4/1961; eliminated 4/1962 | | NAKINA |
