A runway that's scheduled for major maintenance work later this year had to undergo unscheduled maintenance Thursday morning because of a 1-foot-wide pothole.

As an SFO spokesperson tells SFGate, Runway 28L was shut down this morning for the unscheduled repairs to a "12-inch-wide area." Repairs began sometime before 9 a.m., and they also required the closure of Runway 1R.

Runway 1R is expected to reopen at 11:30 a.m., with 28L hopefully back open by 3 p.m. The issue has caused a major backup at the airport as planes are trying to take off.

As the airport tells ABC 7, the pothole was spotted before dawn today, and isn't big enough to cause a major accident but could potentially make for a bump in a landing.

The same runway, 28L, is scheduled to be shut down for 20 days in September to "construct a new base layer below the runway surface," as the airport announced two weeks ago. That closure is expected to cause delays throughout the month after 9 a.m. on most days.

The single pothole, meanwhile, has triggered nationwide flight delays and some flight cancellations. ABC 7's Amy Hollyfield was at the airport where a number of Southwest passengers were dealing with rebookings due to flight cancelations and delays.

Also, Alaska Airlines is reportedly diverting flights to Oakland Airport in the meantime.