CHICAGO: Southwest Airlines plans to continue adding new markets to its network after announcing about 10 new destinations during the pandemic, CEO Gary Kelly said on Thursday, a strategy that threatens to put rivals like United Airlines on defense.

Low-cost carrier Southwest recently unveiled plans to launch service at Chicago O'Hare and Houston's George Bush Intercontinental Airport, two United hubs, next year, as well as places like Palm Springs, California, and Sarasota, Florida.

On Thursday it added Jackson, Mississippi, to the list.

"There's more coming," Kelly said at a virtual Wings Club event.

He said the marginal cost of adding a flight is "very modest," assuming there is demand for the route, given the airline's current 20% overstaffing and hundreds of parked airplanes as overall travel demand remains depressed.

The destinations are intended to be permanent additions to Southwest's network, he said.

Asked whether the carrier had seen a rise in cancellations following its decision to stop blocking middle seats, Kelly said there had been an increase but attributed it to the spike in COVID-19 cases across the country rather than the middle seat policy change, which took effect this month.