Pilots on a Southwest Airlines flight attempting to land at Chicago’s Midway Airport were forced to climb back into the sky to avoid another aircraft crossing the runway.

Weeks after major issues led to thousands of flights canceled during the holidays, Southwest Airlines is facing another problem.

Thousands of flights across the U.S. were canceled or delayed after a system that offers safety information to pilots failed.

A large swath of the U.S. braced for a dangerous mix of sub-zero temperatures, howling winds and blizzard conditions already hammering the Northwest and expected to disrupt plans for millions of holiday travelers.