| Separation Standard | Navigation Capability | Transponder Capability | Suffix |
| RVSM | Any | Failed transponder | /H |
| Any | Failed Mode C | /O | |
| No RNAV, No GNSS | Transponder with Mode C | /W | |
| RNAV, No GNSS | Transponder with Mode C | /Z | |
| GNSS | Transponder with Mode C | /L | |
| Non-RVSM | No DME | No transponder | /X |
| Transponder, no Mode C | /T | ||
| Transponder with Mode C | /U | ||
| DME | No transponder | /D | |
| Transponder, no Mode C | /B | ||
| Transponder with Mode C | /A | ||
| TACAN | No transponder | /M | |
| Transponder, no Mode C | /N | ||
| Transponder with Mode C | /P | ||
| RNAV, no GNSS | No transponder | /Y | |
| Transponder, no Mode C | /C | ||
| Transponder with Mode C | /I | ||
| GNSS | No transponder | /V | |
| Transponder, no Mode C | /S | ||
| Transponder with Mode C | /G |
Reference: https://www.faa.gov/documentLibrary/media/Order/7110.65Z_ATC_Bsc_w_Chg_1_dtd_12-2-21.pdf
Note: (COC reference for Mode C?) Note: Something about Basic RNAV capability and not necessarily being able to do RNAV SIDs/STARS/IAPs but Q/T routes maybe ok?