| I | Island |
| IAC | Instrument Approach Chart |
| IAF | Initial Approach Fix |
| IAL | Instrument Approach and Landing Chart |
| IAP | Instrument Approach Procedure |
| ]AS | Indicated Airspeed |
| IAWP | Initial Approach Waypoint |
| IBN | Identification Beacon |
| ICAO | International Civil Aviation Organisation |
| IDENT | Identification |
| IF | Intermediate Approach Fix |
| IFF | Identification Friend or Foe (a military form of SSR) |
| IFR | Instrument Flight Rules |
| IFSS | Intl. Flight Service Station |
| IGS | Instrument Guiding System |
| ILS | Instrument Landing System |
| IM | Inner Marker |
| IMC | Instrument Meteorological Conditions |
| IMP | Imperial Gallons |
| IMT | Immediate/immediately |
| IMTA | Intensive Military Training Area |
| in or INS | Inches |
| INA | Initial approach |
| INBD | Inbound |
| INCERFA | Uncertainty Phase |
| INCL | Inclusive/including |
| INDEFLY | Indefinitely |
| INFO | Information |
| INOP | Inoperative |
| INP | If Not Possible |
| INS | Inertial Navigation System |
| INSTL | Install; Installed: Installation |
| INSTR | Instrument |
| INT | Intersection |
| INTER | Intermittent |
| INTL | International |
| IORRA | Indian Ocean Random RNAV Area |
| IR | Instrument Restricted Controlled Airspace |
| IS | Islands |
| ISA | International Standard Atmosphere |
| ISO | Instead of |
| ITWS | Integrated Terminal Weather System |
| I/V | Instrument/Visual Controlled Airspace |
| IWP | Intermediate Waypoint |
