| 1 | YS | Flamingo Airways Limited | ICAO: KFL, Callsign: Nakuru, IATA designator changed to F7. Subsidiary of Kenya Airways | EAK | AVCODES |
| 2 | YS | Régional Compagnie Aérienne Européenne | ICAO: RAE, Callsign: Regional Europe, IATA Prefix: 977, Name changed to Regional Compagnie Aerienne Europeenne t/a HOP!-R�gional. Designator YS reinstated by IATA. ICAO designator changed from PRS. Formed 04/2001 by merger of Flandre Air, Protues Air and Regional Airlines | F | AVCODES |
| 3 | YS | Proteus Airlines | ICAO: PRB, Callsign: Proteus, IATA Prefix: 977, Name changed to Regional Compagnie Aerienne Europeene on 30 March 2001. | F | AVCODES |
| 4 | YS | Regional Compagnie Aerienne Europeene | ICAO: PRB, Callsign: Proteus, IATA Prefix: 977, Formed from merger of Proteus Airlines, Flandre Air, and Regional Airlines. | F | AVCODES |
| 5 | YS | Regional Compagnie Aerienne Europeenne t/a HOP!-Régional | ICAO: RAE, Callsign: Regional Europe, IATA Prefix: 977, Merged into Air France w.e.f. 01 Septmerb 2019. Name changed from R�gional Compagnie A�rienne Europ�enne. Designator YS reinstated by IATA. ICAO designator changed from PRS. Formed 04/2001 by merger of Flandre Air, Protues Air and Regional Airlines | F | AVCODES |
| 6 | YS | Flightlink Limited | ICAO: FLZ, Callsign: Flightlink, | EAT | AVCODES |
| 7 | YS | Youngstown & Suburban Ry. Co. | 4/1938-4/1970 | | NAKINA |
| 8 | YS | Youngstown & Southern Ry. Co. | 1/1975-1/1980; eliminated 7/1993; 1/1994-7/2005 (not listed) | | NAKINA |
| 9 | YS | Youngstown & Suburban Ry. Co. | 4/38-1/52; 10/57-4/70 | | NRHS |
| 10 | YS | Youngstown & Southern Ry. Co. | 1/75-1/80; eliminated 7/93; 1/94-7/2000 | | NRHS |
| 11 | YS | (PLW) PL&W RAILROAD CO., INC. [YOUNGSTOWN & SOUTHERN RWY.; YOUNGSTOWN & SUBURBAN RWY. CO.] | | | PWRC |
| 12 | YS | Youngstown and Southern Railway | | | RSRV |
| 13 | YSAA | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 14 | YSAB | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 15 | YSAD | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 16 | YSAH | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 17 | YSAK | | City: Yuzhno-Sakhalinsk | RUS | TRAFFIC |
| 18 | YSAL | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 19 | YSAM | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 20 | YSAM | YANEZ SAIZ, ABRAHAM | | | SCAC4 |
| 21 | YSAZ | NIPPON LINER SYSTEM | | | PWRC |
| 22 | YSAZ | Nippon Liner System Limited | | | RSRV |
| 23 | YSAZ | NIPPON LINER SYSTEM | | | SCAC4 |
| 24 | YSB | YORKE & SON BARGE | | | PWRC |
| 25 | YSB | YORK & SOU BARGE | | | SCAC4 |
| 26 | YSCC | YOUNG SEA CARGO CORP. | | | SCAC4 |
| 27 | YSCL | YUYO STEAMSHIP CO LTD, TOKYO JAPAN | | | SCAC4 |
| 28 | YSCM | YOBEL SUPPLY CHAIN MANAGEMENT INC | | | SCAC4 |
| 29 | YSCU | YANGHAI SHIPPING CO LTD | | | SCAC4 |
| 30 | YSDA | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 31 | YSDF | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 32 | YSDU | YASUDA LOGISTICS CORPORATION | | J | BIC |
| 33 | YSDU | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 34 | YSDU | Yamashita-Shinnihon Line | | | RSRV |
| 35 | YSDU | YASUDA WAREHOUSE CO LTD, THE | | | SCAC4 |
| 36 | YSDX | The Youngstown Steel Door Co. | added 10/1976; 1/1980; eliminated 1/1983 | | NAKINA |
| 37 | YSDX | The Youngstown Steel Door Co. | 1/80; eliminated 1/83 | | NRHS |
| 38 | YSDX | YOUNGSTOWN STEEL DOOR CO. | | | PWRC |
| 39 | YSDX | Youngstown Steel Door | | | RSRV |
| 40 | YSET | Y SEVEN E (Y7E) TRANSPORT INC | | | SCAC4 |
| 41 | YSFD | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 42 | YSFF | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 43 | YSFM | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 44 | YSHL | YISHUN LOGISTICS (USA) INC | | | SCAC4 |
| 45 | YSIC | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 46 | YSIC | YOUNKIN & SONS INC | | | SCAC4 |
| 47 | YSIP | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 48 | YSJU | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 49 | YSJU | Yamashita-Shinnihon Line | | | RSRV |
| 50 | YSLD | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 51 | YSLM | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 52 | YSLN | YOU SUNG LINE | | | SCAC4 |
| 53 | YSLR | Yolo Shortline R.R. Co. | added 4/1991; eliminated 7/1991; 1/1994-7/2005 | | NAKINA |
| 54 | YSLR | Yolo Shortline R.R. Co. | added 4/91; eliminated 7/91; 1/94-7/2000 | | NRHS |
| 55 | YSLR | YOLO SHORTLINE RAILROAD COMPANY | | | PWRC |
| 56 | YSLR | Yolo Shortline Railroad | | | RSRV |
| 57 | YSLR | YOLO SHORTLINE RAILROAD CO | | | SCAC4 |
| 58 | YSLR | Yolo Shortline R.R. Co. | | USA | TRAFFIC |
| 59 | YSLT | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 60 | YSLU | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 61 | YSLU | Yamashita-Shinnihon Line | | | RSRV |
| 62 | YSLU | YAMASHITA SHINIHON STEAMSHIP CO | | | SCAC4 |
| 63 | YSLW | YELLOWBLUE SHIPPING LTD | | | SCAC4 |
| 64 | YSLZ | (YSLU) YAMASHITA-SHINNIHON LINE | | | PWRC |
| 65 | YSLZ | Yamashita-Shinnihon Line | | | RSRV |
| 66 | YSLZ | YAMASHITA-SHINNIH | | | SCAC4 |
| 67 | YSMS | YOUR SPORTS MEMORABILIA STORE | | | SCAC4 |
| 68 | YSMX | Panama Gypsum Co. | added 1/1962; 7/1965-1/1975; eliminated 4/1976 | | NAKINA |
| 69 | YSMX | Canadian Gypsum Co., Ltd. | added 4/1976; 1/1980; eliminated 4/1991 | | NAKINA |
| 70 | YSMX | Panama Gypsum Co. | added 1/62; 7/65-1/75; eliminated 4/76 | | NRHS |
| 71 | YSMX | Canadian Gypsum Co., Ltd. | added 4/76; 1/80; eliminated 4/91 | | NRHS |
| 72 | YSMX | RETIRED09-29-92 ATP (1676) [CANADIAN GYPSUM CO. LTD.; PANAMA GYPSUM CO.] | | | PWRC |
| 73 | YSMX | Canadian Gypsum | | | RSRV |
| 74 | YSNA | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 75 | YSRR | YOUNGSTOWN & SOUTHEASTERN RAILROAD CO., INC. | | | PWRC |
| 76 | YSRR | YOUNGSTOWN & SOUTHEASTERN RAILROAD | | | SCAC4 |
| 77 | YSSW | YANAM SERVICES SA | | | SCAC4 |
| 78 | YST | YOUNGSTOWN SHEET & TUBE CO. | | | PWRC |
| 79 | YST | YOUNGS TRANSPORTATION | | | SCAC4 |
| 80 | YSTC | Yverdon-Sainte Croix | | CH | TRAFFIC |
| 81 | YSTD | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 82 | YSTK | YORK STATION TRUCKING | | | SCAC4 |
| 83 | YSTM | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 84 | YSTN | YELLE, SYLVAIN TRANSPORT | | | SCAC4 |
| 85 | YSTP | YOSEMITY SAM TRANSPORT | | | SCAC4 |
| 86 | YSTR | YES TRANSPORT | | | SCAC4 |
| 87 | YSTS | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 88 | YSTT | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 89 | YSTU | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 90 | YSTU | Yamashita-Shinnihon Line | | | RSRV |
| 91 | YSTX | The Youngstown Sheet & Tube Co. | 8/1920-4/1970; eliminated 7/1972; 1/1975-1/1980 | | NAKINA |
| 92 | YSTX | The Youngstown Sheet & Tube Co. | 4/38-1/80 | | NRHS |
| 93 | YSTX | RETIRED 02-19-91 FET (ACI 1677) [YOUNGSTOWN SHEET & TUBE CO.] | | | PWRC |
| 94 | YSTX | Youngstown Sheet and Tube | | | RSRV |
| 95 | YSUF | YAMASHITA-SHINNIHON LINE | | | PWRC |
| 96 | YSVR | Yellowstone Valley R.R. Inc. | added 4/2008 | | NAKINA |
| 97 | YSVR | YELLOWSTONE VALLEY RAILROAD, INC. | | | PWRC |
