Aviation Alphabet & Codes Guide

Indicates the aircraft has been hijacked or is under unlawful interference. ATC will confirm with discrete questioning. Do NOT squawk 7500 by accident — it triggers immediate security response.

Indicates loss of two-way radio communication. ATC will attempt contact on all frequencies, use light signals, and provide radar vectors. Pilot should follow lost-comm procedures (FAR 91.185).

General emergency. Squawk 7700 to declare an emergency of any kind — engine failure, medical emergency, fuel emergency, etc. Triggers priority handling and alerts all ATC facilities.

Default transponder code for VFR flight in the US when no specific code has been assigned. All VFR aircraft not in contact with ATC should squawk 1200.

Default VFR code used in many countries outside the US (ICAO standard). Check the country-specific AIP for local VFR squawk codes.

Used when entering a radar environment from a non-radar area, or when no specific code has been assigned by ATC in many international operations.

Reserved code. In the US, typically not assigned to civil aircraft. Military operations may use this and other low-range codes.

Used by FAA flight inspection aircraft calibrating navaids. If you see this code on radar, it is an FAA aircraft checking ILS, VOR, or other navigation equipment.

Discrete code reserved for military operations within the US NAS. Assigned by military ATC or ARTCC when operating under specific military procedures.

Reserved for military interceptor aircraft under DoD direction. Civil aircraft must NEVER squawk 7777 — it identifies the aircraft as an active military interceptor.

Recorded weather and airport info broadcast on a loop. Identified by letter (e.g., "Information Alpha"). Pilots must acknowledge the current ATIS letter on initial contact.

Standardized weather observation issued every hour (or as a SPECI for significant changes). Includes wind, visibility, clouds, temperature, dewpoint, and altimeter setting.

Weather forecast for a specific airport, covering a 24-30 hour period. Uses the same format as METARs but with forecast modifiers like TEMPO, BECMG, and PROB.

Advisory notice containing information on hazards, changes, or temporary conditions at an airport or along a route. Mandatory preflight reading. Formerly "Notice to Airmen."

Ground-based radio navigation aid that transmits 360 radials. Pilots tune the frequency and select a radial to navigate TO or FROM the station. Being phased out in favor of GPS.

Low-frequency radio beacon used with an ADF (Automatic Direction Finder) receiver. Points toward the station. Oldest form of radio navigation still in limited use.

Precision approach system providing lateral (localizer) and vertical (glide slope) guidance to a runway. Categories I, II, and III define minimum visibility requirements.

Radio navigation system that measures slant-range distance between aircraft and a ground station. Often co-located with VOR or ILS. Displays distance in nautical miles.

Satellite-based navigation. WAAS-enabled GPS can provide approach capability down to 200 feet above the runway (LPV approaches). Now the primary navigation method for most GA pilots.

Navigation method allowing flight on any desired path, not limited to ground-based navaids. GPS-based RNAV is standard in modern aviation. Required for many airspace and approach procedures.

Published departure procedure that provides routing from the runway to the en-route airway system. Simplifies clearances and reduces radio congestion.

Published arrival procedure connecting the en-route airway system to an approach procedure at the destination airport. Includes altitude and speed restrictions.

Temporary airspace restriction for security (presidential movement), disasters, sporting events, or military operations. Violating a TFR can result in certificate action and interception.

Frequency used for self-announce position reports at non-towered airports. Often 122.8 or the listed frequency on the chart. All pilots in the area should monitor and broadcast.

Radio frequency at non-towered airports for airport advisory (wind, runway in use) and services (fuel, taxi). Often the same frequency as CTAF.

Weather report submitted by pilots in flight. Includes turbulence, icing, visibility, and cloud layers. Extremely valuable for other pilots and meteorologists.

Weather advisory for severe conditions: thunderstorms, severe turbulence, severe icing, volcanic ash, or tropical cyclones. Affects all aircraft.

Weather advisory for moderate conditions: moderate turbulence (Tango), moderate icing (Zulu), and IFR/mountain obscuration (Sierra). Primarily for small aircraft.

Airborne system that detects nearby transponder-equipped aircraft and issues traffic advisories (TA) and resolution advisories (RA). Mandatory on Part 121 aircraft.

GPS self-check function that verifies satellite geometry is adequate for IFR navigation. Must be predicted available for GPS approaches. Requires 5+ satellites.

Does NOT mean "yes" or "affirmative." It only means the message was received.

Short for "will comply." Stronger than Roger — implies action.

Use instead of "yes" on the radio. ICAO standard uses "Affirm."

Clear and unambiguous. Never say "no" on the radio — use "Negative."

Never say "repeat" — in military communications, "repeat" means fire again.

ATC uses this to verify you received a clearance correctly. Readback is mandatory for runway assignments, altitudes, and headings.

Example: "Squawk 4523" means set transponder to 4523. "Squawk ident" means press the IDENT button.

"Cleared for takeoff," "Cleared to land," "Cleared ILS Runway 27." This is an authorization, not a suggestion.

"Hold short Runway 28L" — stop before the hold short line. Requires mandatory readback.

Formerly "position and hold" in the US. You are ON the runway but NOT cleared for takeoff.

Mandatory instruction. Apply full power, pitch up, follow published missed approach or ATC instructions.

Pilots can always say "unable" for safety. Example: "Unable maintain 250 knots, minimum clean speed 270."

Said three times: "Pan-Pan, Pan-Pan, Pan-Pan." Examples: fuel concern, sick passenger, minor system failure.

Said three times: "Mayday, Mayday, Mayday." Highest priority. Engine failure, fire, structural failure.

Creates a highlighted return on the controller's radar scope for positive identification.

"Maintain 6,000" means fly at 6,000 feet. "Maintain 250 knots" means hold that speed.

"Contact approach on 124.8" means switch to that frequency and check in.

Different from "contact." Just listen — they will call you when ready.

Saying "Roger" when you mean "Wilco"

Why it matters: Roger only means "received." If ATC tells you to do something and you reply "Roger," you have not confirmed you will comply. Use "Wilco" (will comply) or read back the instruction.

Fix: Rule: If it is an instruction (climb, descend, turn, hold short), read it back or say Wilco. If it is just information (traffic advisory, weather update), Roger is fine.

Saying "repeat" instead of "say again"

Why it matters: In military communications, "repeat" means "fire again" (as in artillery). While this is less critical in civil aviation, the standard phraseology is "say again" to avoid any ambiguity.

Fix: Always use "say again" to request a repeat of the last transmission. It is correct, professional, and unambiguous.

Blocking the frequency with long transmissions

Why it matters: Holding the push-to-talk button while thinking of what to say blocks the entire frequency. Other aircraft cannot transmit emergencies or position reports while you are keyed up.

Fix: Plan what you will say BEFORE pressing the PTT button. Keep transmissions brief: who you are, where you are, what you want. Release the button between thoughts if needed.

Not using your callsign

Why it matters: Starting a transmission without your callsign ("Tower, requesting runway change") forces ATC to ask who is calling. At busy airports, this wastes time and causes confusion.

Fix: Always include your callsign in every transmission: "Tower, Cessna Three Alpha Bravo, request runway change to Two Eight Right."

Pronouncing 9 as "nine" instead of "niner"

Why it matters: "Nine" can sound like "nein" (German for no) or "five" in poor radio conditions. "Niner" is unambiguous in all conditions and languages.

Fix: Always use the ICAO pronunciations: tree (3), fife (5), niner (9). These exist for a reason — they have been tested across dozens of languages and accent types.

Not monitoring the frequency before transmitting

Why it matters: Stepping on (transmitting over) another pilot or controller is unprofessional and potentially dangerous. It blocks both transmissions.

Fix: Listen for at least 5-10 seconds before your first transmission on any new frequency. Ensure the frequency is clear before pressing PTT.

Using non-standard phraseology

Why it matters: Casual language ("We're going to head on over to runway 28") is ambiguous and unprofessional. Standard phraseology exists because each phrase has been tested for clarity.

Fix: Study and use the standard phrases: "Taxi to Runway Two Eight" not "head over to 28." "Cleared to land" not "OK to land." Precision in language equals precision in flying.