All flights going in and out of Heathrow Airport in London were cancelled or delayed Tuesday due to technical difficulties with their air traffic control service that lasted several hours.

The issue had ripple effects across the world, including at Toronto Pearson International Airport where a number of flights arriving from and departing for Heathrow were cancelled.

NATS, the provider of air traffic control services at Heathrow, first reported the problem around 9 a.m. ET, saying on X that they were investigating a technical issue “which is causing some disruption to flight departures.”

A few hours later, Heathrow Airport staff posted on X that both arriving and departing flights were affected by the issue. Travellers were advised to check with their airlines for the latest information on their flights and only travel to the airport if their flight was confirmed.

The air traffic control service @NATS is experiencing a technical issue which is impacting arriving and departing flights across UK airports.

We are supporting our local NATS team in their efforts to resolve the issue as quickly as possible.

We apologise to those affected by… pic.twitter.com/ji2LyCdL3T

— Heathrow Airport (@HeathrowAirport) September 8, 2026

Around 2:30 p.m. ET, NATS officials said the technical issue took longer than anticipated to fix, but was resolved. They said they were working hard to clear the backlog of flights.

More to come