Do Airplanes Have Horns? Yes, and Here Is What Each One Means

Yes, airplanes have horns, but nobody honks them at traffic. Airliners use horns and other loud tones as warnings and as a way to get the attention of people outside the aircraft.

Most of these sounds are meant for the flight crew and ground staff, not for passengers. The rest of this page covers the horn outside the nose, the alerts on the flight deck, and what each one is for.

The ground call horn

The one true horn on a Boeing 737 sits in the nose wheel well. It is called the ground call horn, and it is built to be heard by people standing outside the aircraft.

According to a Boeing 737 systems reference, it also sounds on its own for two fault conditions: an overheat in the electronics bay, or the inertial reference systems running on DC power. A fire bell can ring in the wheel well as well.

The reason is simple. A mechanic or ramp worker walking around a parked airliner may be nowhere near the cockpit, so the warning has to be outside.

Ground crews can also talk to the flight deck by plugging a headset into the aircraft, which is far clearer than shouting over a running auxiliary power unit.

Warning sounds on the flight deck

Inside the cockpit, the sounds are alerts. A 737 reference lists the fire bell, takeoff configuration warning, cabin altitude, landing gear configuration, overspeed, stall warning, GPWS and TCAS among its aural warnings.

Many of them are not a design choice. U.S. airliner rules require an audible warning for specific problems.

The takeoff warning horn

This is the one that most often gets pilots’ attention. The rule says the system must warn the pilots automatically during the initial takeoff roll if the airplane is in a configuration that would not allow a safe takeoff.

That covers flaps or leading edge devices outside the approved takeoff range, and spoilers, speed brakes or trim in the wrong position.

The warning continues until the configuration is fixed, the pilot ends the takeoff roll, the airplane rotates, or the pilot manually silences it.

Because the warning is tied to the start of the takeoff roll, a horn there is a chance to catch a setup mistake while the airplane is still on the runway and still slow. After rotation, the rule no longer requires it.

Landing gear, cabin and speed alerts

The gear warning is required to sound continuously, or repeat periodically, if a landing is attempted without the gear locked down. It must come early enough to lower the gear or go around.

The cabin rule is an alert when cabin pressure altitude goes above 10,000 feet. The regulation says “alert” and does not specify a sound.

For speed, turbine airplanes need an aural warning that differs distinctively from the warnings used for other purposes. That is why an overspeed sounds nothing like a gear warning.

Loud is deliberate. One reference notes aural warnings are set so they stay audible at the highest ambient noise levels the airplane is expected to see.

The stall warning

Stall warning is the one alert regulators treat most carefully. Under 14 CFR 25.207 it must be clear and distinctive to the pilot, in straight and in turning flight.

It can come from the airplane’s own aerodynamics, such as buffet, or from a device. A visual-only device that needs the crew to look inside the cockpit is not acceptable by itself.

Once the warning starts, it must continue until the angle of attack is reduced to roughly where the warning began. That is why a stall warning does not blink off the moment a pilot nudges the controls.

How alerts are ranked: red, amber and advisory

Sounds are only half of the system. The FAA sorts every flight deck alert into three levels, and color tells the crew which level they are looking at.

For warnings and cautions, the same rule asks for timely attention-getting cues through at least two different senses. A sound plus a light is the usual pairing.

Advisories do not carry that requirement, which is why a routine advisory is usually quiet while a red warning is hard to miss.

When the horn becomes a voice

Modern airliners also talk. The Boeing 737 reference gives the aural warnings a strict priority order, so the most urgent message always wins when two trigger at once.

Windshear tops the list, followed by the “pull up” sink rate and terrain warnings. The V1 callout, minimums, bank angle and TCAS alerts come further down, with a TCAS resolution advisory ranked above a traffic advisory.

The same reference lists automatic radio altimeter callouts on later 737 models, such as “500,” “100,” “50” and “minimums,” with the exact set being a customer option.

Those voices exist for the same reason the horns do. A pilot who is busy flying the airplane can hear a message without looking away from the instruments.

Why airplanes do not honk like cars

A horn on a road warns other drivers. In the sky, that job belongs to radio calls to controllers and the collision-avoidance system, and the TCAS and GPWS voices are on the same list of cockpit aural warnings.

So the sounds that exist are aimed at the crew and the ground team, and each one is different enough that pilots know the problem before they look at a panel. For more on the displays behind those sounds, see our guide to cockpit instruments.