SAN FRANCISCO—Two of San Francisco’s International Airport’s four runways were closed for about eight hours on Thursday, April 11 after crews found a foot-deep depression in one of them. The closure resulted in at least 300 flights being delayed.

The pothole, which was initially described as a “12-inch pavement depression,” was found on runway 28L near the intersection with runway 1R during an inspection early Thursday morning. SFO tweeted an alert, stating “28L closed for repair. 1R will also close during repair. Work started at 0800. 28L to remain closed through 1500 and 1R closed from 0900- 1130 to allow repair of pothole on 28L. Expect delays.”

The pothole was in a spot that had already been scheduled for a major repair this fall. In a press release on March 19, SFO announced plans to close runway 28L for 20 days in September to construct a new base layer below the runway surface.

Both runways were closed until the afternoon, with Runway 1R re-opening around noon, while 28L remained closed for an additional two hours as repairs were being made. Since 28L is used for arrivals and 1R for departures, delays began at 25 minutes and grew throughout the morning.