It follows an incident at London’s Gatwick Airport in December, which descended into chaos as drones disrupted pre-Christmas flights for 33 hours, causing approximately £50 million ($64.5 million) in losses.

Authorities warned that flying drones without obtaining permission is subject to legal liability as per UAE laws.

— Dubai Media Office (@DXBMediaOffice) February 15, 2019

Dubai is the world’s busiest international airport, handling about 90 million passengers last year, the Wall Street Journal reports. An official in Dubai said Friday’s airport closure was caused by “a guy in the desert” operating a drone. It wasn’t immediately clear if the person responsible was arrested. No one was ever arrested for the Gatwick drone disruption, which canceled 1,000 flights and affected more than 140,000 passengers.

Drone activity is an increasing worry for airport administrators. In January, both London Heathrow and Newark Liberty International Airport in New Jersey had to briefly stop flights after drone sightings. Their mere presence near an airfield can dramatically disrupt commercial air travel. The U.S. government wants to be able to track drones and identify their users in real time, but rules are years away from becoming final.

Until aviation authorities can figure out how to keep people from flying drones near airports, Gatwick is planning an “airport drone incursion rehearsal” — a drone drill — to be better prepared for future incidents.