Gatwick Airport, the UK’s second busiest airport after London Heathrow, has installed 2,000 battery-powered iBeacons for indoor navigation and passenger tracking.

Available across Gatwick Airport’s two terminals, the system is accurate up to three meters, much more reliable than GPS and enables an augmented-reality wayfinding tool so passengers can be shown directions in the camera view of their mobile device.

It could be used to inform passengers they’re running late and help them avoid missing flights.

Conceivably, Gatwick Airport could also take advantage of iBeacons for efficient queue management and to reduce congestion by being able to determine whether to offload luggage if a late passenger is far away.

According to the airport, they won’t be collecting any personal data from the beacons with the exception of “generic information on ‘people densities’ in different beacon zones.”

Deployed in just three weeks, iBeacons form part of Gatwick’s £2.5 billion (about $3.1 billion) transformation initiative. The technology is currently being integrated into some of the Gatwick apps.

The airport is in discussion with other airlines to enable the indoor positioning and wayfinding tools to also feature on their apps and services.

According to Gatwick:

Airlines could go further—and with the consent of their passengers—may send reminders on their airline app to late running passengers, for example, or find out where they are and make an informed decision on whether to wait or offload their luggage so the aircraft can take off on time.

The lack of satellite signals makes road-based navigation systems, like Apple Maps, unreliable indoors. That’s why Apple has developed inexpensive iBeacons, which are tiny battery-powered Bluetooth transmitters.