United Airlines flights at San Francisco International Airport (SFO) were grounded Wednesday evening due to a “technology issue,” the airline said in a statement. As of 6:20 p.m., the ground stops for United flights have been lifted,

The outage began just after 6 p.m. ET and was resolved a few hours later, though delays are expected to continue into the night.

United Airlines resolved the system disruption that delayed over 1,000 flights, but residual delays are expected and the cause is unknown.