(Undated) -- Southwest Airlines cancellations are continuing to cause problems at Texas airports. Almost 600 Southwest flights have been canceled today, and more than 500 scheduled for tomorrow are already canceled as well. U.S. Transportation Secretary Pete Buttigieg says the cancellations are a "system failure," and called on Southwest to give "adequate compensation" to the stranded passengers. The Dallas-based airline is facing a federal investigation into whether it violated its customer service plan.