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Squawk code · emergency

Squawk 7400: Unmanned aircraft lost link

Squawk 7400 indicates an unmanned aircraft whose control link with its ground pilot has been lost.

Squawk 7400 means a remotely piloted aircraft has lost its control link. It tells controllers the drone is flying a pre-programmed lost-link procedure rather than being steered by its pilot on the ground.

What 7400 means

Large unmanned aircraft, such as military and border-patrol drones, fly in the same airspace as crewed aircraft and carry transponders. Their pilots sit in a ground control station connected by a radio or satellite datalink. If that link fails, the aircraft cannot receive commands. The FAA assigned code 7400 in the US for this case, and ICAO recommends the same code internationally. The aircraft (or its pilot, before the link drops) sets 7400 so radar displays flag it.

What happens next

Every lost-link procedure is planned before flight and filed with or coordinated with air traffic control. Typically the aircraft will:

  • climb or descend to a pre-set altitude,
  • fly a pre-set route or orbit while the crew tries to restore the link, and
  • if the link is not restored, return to a recovery area or land at a planned site.

Controllers use the published plan to keep other traffic away. In most cases the link comes back within minutes and the aircraft returns to its normal code.

How 7400 appears on heywhatsflying

Because 7400 is rare and specialized, we list it among notable squawks rather than as a headline emergency. If you see it, the aircraft is most likely a large drone such as an MQ-9 near a military range or the southern border. Many drones do not broadcast ADS-B at all, so this code is seen far less than it occurs. See why military aircraft show or don't for context.

Common myths

  • "A lost-link drone is out of control." No. It is following a programmed, pre-coordinated plan.
  • "Hobby drones squawk 7400." Small consumer drones do not carry transponders and are not allowed to broadcast ADS-B Out under FAA rules.

Related codes: 7600 (radio failure for crewed aircraft) and 7700 (general emergency). See the full squawk code index.

Questions

What aircraft use squawk 7400?

Large unmanned aircraft that carry transponders, such as military and government drones. Small consumer drones do not carry transponders.

Is a drone squawking 7400 dangerous?

It is flying a lost-link procedure planned and coordinated before the flight, so controllers know where it will go. The link is often restored within minutes.