| Abbreviation | Definition |
|---|---|
| CIR | Customer Inspection Required |
| CIRA | Central Illinois Regional Airport |
| CIS | Cabin Interphone System |
| CIS | Crew Information Systems |
| CIS-MSFSM | Crew Information Systems- Maintenance System File Server Module |
| CISS | Configurable Integrated Surveillance System |
| CISS | Configurable Integrated Surveillance System (See ISS) |
| CIT | Captain Instrument Tie |
| CIT | Captain Instrument Transfer |
| CITEXT | Computer Integrated Text |
| CJ | Cobra Jet |
| CJ | Corporate Jetliner |
| CKD | Checked |
| CKPT | Cockpit |
| CKS | Checks |
| CL | Centerline |
| CL | Centerline Lights |
| CLAAC | Commission latino-américaine de l’aviation civile (French: LatiAmerican Civil Aviation Commission) |
| CLB | Climb |
| CLN | Clean |