| Abbreviation | Definition |
|---|---|
| IHP | Indicated HorsePower |
| IHTV | Interim Hypersonics Test Vehicle |
| IHX | Interloop Heat Exchanger |
| IHY | International Heliophysics Year |
| IIG | Interrange Instrumentation Group |
| IIS | Inspection Item Sheet |
| IIT | Indian Institute of Technology |
| IITCS | Igloo Internal Thermal Control Section |
| ILA | Instrument Landing Approach |
| ILAS | Instrument Landing Approach System |
| ILC | Initial Launch Capability |
| ILC | Intermediate Loads Cycle |
| ILC | International Latex Corporation |
| ILCCS | Integrated Launch Control and Checkout System |
| ILF | Intelligent Life Forms |
| ILLUM | Illuminate |
| ILOAD | Initialization Load |
| I-LOS | Initial Data Load |
| ILP | Integrated Logistics Panel |
| ILS | Inertial Landing System |