| 1 | R4 | State Transport Company of Russia | ICAO: SDM, Callsign: Russia, IATA Prefix: 948, Merged with Pulkovo Aviation Enterprise FV/PLK. Designator R4 reinstated by IATA | RUS | AVCODES |
| 2 | R4 | Tulpar Avia Service | ICAO: TUX, | KZ | AVCODES |
| 3 | R4 | Reliable Unique Services Aviation LLC | ICAO: RLB, Callsign: Reliable, IATA Prefix: 827, IATA designator changed from R6* | AM | AVCODES |
| 4 | R4 | Real Tonga Airline | ICAO: RLT, Callsign: Real Tonga, Designator R4 recalled by IATA. | TO | AVCODES |
| 5 | R4C | Rail4Chem Eisenbahnverkehrsgesellschaft mbH | Essen | D | privat-bahn.de |
| 6 | R4C | Rail4Chem (BASF AG, Bertschi AG, HOYER GmbH, VTG-LEHNKERING AG) | | D | TRAFFIC |
| 7 | R4U | Rail4You | | D | TRAFFIC |
