London's Heathrow Airport reopened on Saturday after a power outage at one of the world's busiest airports the previous day caused widespread chaos and cancellations.

London’s primary airport, the main gateway for U.S. travelers to Europe, expects disruption for days as a result of a fire at an electrical substation. At least 1,300 flights were affected.

London’s Heathrow Airport, one of the world’s busiest, announced a complete shutdown all day Friday due to a “significant power outage” as a result of a large fire nearby and warned that “significant disruptions” can be expected over the coming days.