The Phoenix Sky Harbor International Airport is experiencing a partial power outage that is impacting major airlines, leading to canceled and delayed flights, a tweet from the airport says.

The outage affected services at two terminals, with American Airlines Group Inc and Southwest Airlines Co experiencing “significant flight impacts,” the airport said on Twitter.

Southwest Airlines, which carries the most passengers at Phoenix Sky Harbor, canceled more than 30 flights by late morning and diverted another 15 to other cities, the carrier said. “Significant” delays and additional grounded flights are expected, it said.

American Airlines, the No. 2 carrier at Phoenix, has canceled 12 flights, with another 32 delayed.