As a pilot, it’s important to memorize the different emergency squawk codes. As a non-pilot, you might be thinking “whats the emergency and why are people squawking?”. In this post we’ll explain exactly what a transponder is and what it does, and also what these Squawk codes are and what they mean.

A transponder is a device on the aircraft that communicates with ATC radar. There are 3 emergency transponder codes reserved to let ATC know exactly what type of emergency you are having.

7500 – Hijacking

7600 – Lost radio/communications

7700 – General Emergency (Engine Failure, Medical Emergencies, etc)

Simple enough right? So now that you know the codes, if you have an emergency, you just have to remember to put those into your transponder and continue to fly the plane. In this post we’ll discuss what exactly a transponder is and what might happen if you were to have any one of the emergencies listed above.

What is a Transponder?

Before we can put any codes in anywhere, lets first take a look to understand what exactly a transponder is and what it does.

Wikipedia defines a Transponder as “an electronic device that produces a response when it receives a radio-frequency interrogation.”

In English this basically means it is a device in an airplane that sends a signal back to a radar screen in an Air Traffic Control facility. On this radar screen the controllers can see the aircraft’s “Squawk Code”, along with the aircraft’s position, altitude, and its call sign. A simple aircraft transponder looks like the device picture below.

A Simple Aircraft Transponder
A Simple Aircraft Transponder
A Modern Aircraft Transponder

Do All Airplanes Need a Transponder?

No, they are not required equipment on all aircraft. It is however required to fly in specific airspace denoted by “Mode C” on an aeronautical map as well as aircraft operating in Class A, B, and C airspace. This “Mode C Veil” is a 30 nautical mile ring around Class B airspace.

Mode C Veil on an aeronautical map
Mode C Veil on an aeronautical map

A Mode C transponder refers to a device that is equipped with an altitude encode as well as altimeter. ATC Will be able to see the aircraft’s altitude on their radar screens so long as the transponder is in the “ALT” mode, which is the mode it is generally always supposed to be in.

There are some exceptions to the Mode C requirements, those are:

  • Aircraft which were not originally certificated with an engine-driven electrical system or have not been certified with such a system installed. These include balloons, or gliders.

An aircraft may operate without a Mode C transponder within the 30 nautical mile ring, as long as the aircraft:

  • Is outside of Class A, B, and C airspace
  • Is below the ceiling of the Class B or C airspace designated, or is below 10,000 ft MSL, whichever is lower
  • Above 10,000 ft MSL excluding the airspace above the lateral limits of Class B and C airspace

You can also fly into the “Mode C Veil” so long as the pilot has telephoned the radar facility and agreed upon the flights direction and altitude. The pilot will be given a code which will then be told to the controller upon first contact. These approvals are not likely to be given during busy times or during inclement weather.

What Does “IDENT” Mean?

Transponders have a button on them labeled as “Ident”. As a pilot, you will likely hear the following from Air Traffic Control at some point:

  • ATC: “Cessna 144DP, squawk 0257 and Ident”
  • Aircraft: “0257 and Ident, 4DP”

IDENT is a feature on the transponder that basically sends a signal to the Air Traffic Controllers radar screen that says “HEY LOOK AT ME! I’M OVER HERE!” This helps ATC identify exactly which little blip on their radar screen is you.

Modern Aircraft Cockpit

To learn some other common phrases that pilots use when talking to Air Traffic Control, check out our post 11 Things Pilots Say & What They Mean!

Emergency Squawk Codes

There are 3 main emergency squawk codes that can help ATC determine what is happening with you and your aircraft. We’ll dive into them further here.

7500 – Hijacking

If your aircraft has been hijacked, inputting code 7500 is a way of sending a silent alert to ATC to make them aware of your situation without your hijacker knowing.

If you do squawk 7500, you can expect there to be fighter jets scrambled to your position to escort you back to a base of their choosing. Or, in the unlikely event that you do not comply, well, they do come locked and loaded for a reason.

*Note – Do not squawk 7500 just to get a free in-flight airshow, this is frowned upon*

In the event that you are hijacked and your hijacker doesn’t know about these squawk codes. You can set transponder to 7500 but be ready to be quick witted in your replies with ATC. They may likely want to confirm you are squawking 7500, but will keep communications “unassuming” so that nothing escalates the situation further. Be ready to comply with their instructions.

7600 – Lost Radio/Communications

If your radio happens to go out during flight and you can’t contact ATC, what do you do? The first thing would be to put 7600 into your transponder, this way ATC will know that you cannot communicate with them as they are watching you fly through their airspace wondering why this guy isn’t replying.

This is where you as a pilot need to be on high alert, looking for other aircraft in the sky, especially around a busy airport. ATC is likely communicating with other pilots in the air about you, but it is very difficult to spot even other airplanes from the sky so be sure to keep your eyes outside.

Good thing the FAA has procedures in place for exactly this situation. If your radio has failed, you should squawk 7600 and proceed cautiously to the airport you intend to land at and follow a standard landing pattern entry. This is were a cell phone may come in handy. You may be able to get service at pattern altitude and can call the tower phone number (you should probably save these in your phone) for further instructions.

Be on the lookout for light signals from the control tower. These will be signals clearing you to land or otherwise. Once you have landed, keep looking at the tower for taxi instructions.

Here are the light gun signals and what they mean:

SignalOn GroundIn Flight
Steady GreenClear for TakeoffCleared to Land
Flashing GreenCleared to TaxiReturn to Land
Steady RedStopGive Way
Flashing RedTaxi Clear of RunwayDo Not Land
Flashing WhiteReturn to Rampn/a
Alternating Red & GreenUse cautionUse Caution

7700 – General Emergency

Emergencies in this category can be anything that the pilot deems to be an emergency. This can include but are not limited to:

  • Engine Failure
  • Medical Emergencies (Flight crew or Passenger)
  • Fuel emergencies
  • Fire in the cockpit
  • Landing Gear problems
  • Pressurization problems
  • Flight control problems
  • VFR flight into IMC conditions

If you are having an in-flight emergency you will likely already be talking to someone and declared an emergency before you even squawk 7700. This code however can alert other controllers in the area that are not speaking directly with you. If this code is put in, any controllers in the area are alerted and will get ready to coordinate assistance in any way that they can. If in an emergency situation, use ATC, they are a great resource and are there for you.

Vintage ATC Facility

If you’re looking to get started in flight training and are curious about what jobs are out there we’ve got 2 posts that you should check out. The first is the Top 7 Pilot Jobs to Build Hours which will give you insight into what jobs you may need to do before going to the airlines, if that is your goal. The other is looking into what upper level pilot jobs actually pay in our post Here’s How Much Pilots Really Get Paid.

Simple Ways to Remember Squawk Codes

These are simple rhymes you can use to memorize what the different squawk codes mean.

  • 75 – Let the other guy drive (Hijacking) – 7500
  • 76 – Plane needs a fix (Broken radio) – 7600
  • 77 – Going to heaven (All other emergencies) – 7700

Related Questions

What does Squawk VFR mean? Squawking VFR basically means that you are an aircraft flying under Visual Flight Rules (VFR). The standard code for VFR flight when no other code has been assigned is 1200.

What are the different types of Transponders?

  • Mode A – equipment transmits an identifying code only.
  • Mode C – equipment enables the ATCO to see the aircraft altitude or flight level automatically.
  • Mode S – equipment has altitude capability and also permits data exchange.

Whether you are a new student pilot or a seasoned aviator, we all need to wear headsets. Check out our Headset Buyers Guide for some equipment that may work for you.