| F |
| F | Fighter (Aircraft) |
| F&AO | Finance & Accounting Office |
| FA | Field Artillery |
| FAA | Federal Aviation Agency |
| FAC | Forward Air Controller/Control |
| FADSID | Fighter Aircraft Delivered Seismic Detector |
| FAE | Field Advisory Effort/Elements |
| FAG | Forward Air Guide |
| FAMF | Floating Aircraft Maintenance Facility |
| FAMREP | Force and Material Report |
| FAN | Forces Armees Neutralist (Laos) |
| FANK | Forces Armees Nationales Khmeres (Khmer Armed Forces) |
| FANSONG | Tracking radar for Soviet SA-2 surface-to-air missile system |
| FAR | Forces Armees du Royaume or Forces Armees Royales (Royal Laotian Forces) |
| FARK | Forces Armees Royales Khmers (Cambodia) |
| FASO | Fleet Air Support Unit |
| FAST | Field Assistance Support Team |
| FASU | Fleet Air Support Unit |
| FASlD | Fixed-Wing Aircraft-Deployed Seismic Intrusion Detector |
| FATOC | Field Army Tactical Operations Center |
| FAX | Facsimile |
| FB | Fuel Barge |
| FDC | Fire Direction/Directional Center |
| FE | Facilities Engineering |
| FEC | Federal Electric Corporation |
| FEN | Federal Stock Number |
| FF | Field Force |
| FFORCEV | Field Force, Vietnam |
| Fighting (wing) position | Area for the wingman in which optimum coverage and maneuverability is achieved in maximum performance maneuvers. |
| FIN | Finance |
| Finger-four formation | A four-plane formation in which the aircraft occupy positions suggested by the four finger tips of either hand, the fingers being held together in a horizontal plane. - also fingertip formation - |
| FIS | Fighter Intercepter Squadron |
| Flak | Antiaircraft fire. |
| FLC | Force Logistical/Logistics Command |
| FLINT | Electronic Intelligence |
| FLIP | Flight Information Publication |
| FLIR | Forward Looking Infrared Radar |
| FLN | Flown |
| FLN | Force de la Liberation Nationale |
| FLR | Forward Looking Radar |
| FLSG | Force Logistical Support Group |
| FLSG-B | Force Logistic Support Group-Bravo |
| FLSU | Force Logistical Support Unit |
| Flt | Fleet |
| FLT | Flight |
| Fluid element | The second or supporting element in fluid four formation, flying in a high or low element position. |
| Fluid-four | Tactical formation having the second element spread in both the vertical and the second element spread in both the vertical and horizontal planes to enhance maneuverability, mutual support and look-out ability. |
| FM | Field Manual |
| FM | Frequency Modulated |
| FM/TM | Field Manuals/Technical Manuals |
| FMF | Fleet Marine Force |
| FMFP | Fleet Marine Force, Pacific |
| FMFPAC | Fleet Marine Force, Pacific |
| FMR | Financial Market Rate |
| FNC | Floating Naval Club |
| FO | Forward Observer |
| FOB | Forward Operating Base |
| FOD | Foreign Object Damage |
| FOM | French Patrol Boats |
| FONECON | Telephone Conversation |
| FORLOGCMD | Force Logistics Command |
| FOUO | For Official Use Only |
| FPJMC | Four Party Joint Military Commission |
| FPJMT | Four Party Joint Military Team |
| FPO | Fleet Post Office |
| FPS | Azimuth Search and Height Radar |
| FR | Field Ration |
| FR | Floating Repair |
| FRAC | First Regional Assistance Command |
| FRAG | Order dispatching single or multiple aircraft sortie. |
| Fragged | Mission directed by fragmentary operational order from higher headquarters. |
| Frd/FRD/Frdly | Friendly |
| FRG | Federal Republic of Germany |
| Front | The individual in the front seat in the F-4 aircraft; in the Navy called the pilot, in the Air Force called the aircraft commander. |
| FRP | Peoples' Revolutionary Party (Communist) |
| FSA | Forward Support Area |
| FSB | Fire Support Base |
| FSCC | Fire Support Coordination Center |
| FSCL | Fire Support Coordination Line |
| FSE | Fire Support Element |
| FSI | Force Structure Increases |
| FSI | Foreign Service Institute |
| FSL | Force Structure List |
| FSN | Federal Stock Number |
| FSO | Foreign Service Officer |
| FSR | Force Service Regiment |
| FSR | Force Structure |
| Ft | Fort |
| FTC | FANK Training Command |
| FTD | Field Training Detachment |
| FTG | Fleet Training Group |
| Ftr/FTR | Fighter (Aircraft) |
| FTS | Field Training Service |
| F.T.S.V. | Forces Terrestres Sud-Vietnam |
| FTX | Field Training Exercise |
| FULRO | United Front for the Struggle of Oppressed Races (Front Unifie de la Luffe des Races Opprimees) |
| FUNK | United National Front of Kampuchea (Cambodia) |
| FUO | Fever of Unknown Origin |
| FW | Free World |
| FW(F) | Free World (Forces) |
| FWA | Free World Allies |
| Fwd/FWD | Forward |
| FWF | Free World Forces |
| FWM | Free World Military |
| FWMA | Free World Military Assistance |
| FWMA(F) | Free World Military Assistance (Forces) |
| FWMAC | Free World Military Assistance Council |
| FWMAF | Free World Military Assistance Forces |
| FWMAO | Free World Military Assistance Office |
| FWMAPC | Free World Military Assistance Policy Council |
| FWMF | Free World Military Forces |
| FY | Fiscal Year |