The man appeared to be having a mental health emergency and was incoherent and not fully aware of his surroundings, authorities said.
No one was injured after two planes were cleared to use the same runway on Saturday morning.
"You obviously don't respect yourself, so why should we?"
The lawsuit claims Southwest shareholders "suffered significant losses" because the airline hid the risks of its outdated technology.
Southwest Airlines is now turning its attention to repairing its damaged reputation after it canceled 15,000 flights around Christmas and left holiday travelers stranded.
Gary Kelly steered Southwest away from its founding "culture and principles," the union's vice president wrote in a scathing letter.
If Thursday is the last day of the Southwest crisis, it will be marked by about 2,350 canceled flights, nearly 60% of the airline’s schedule.
The transportation secretary is the conservative network's scapegoat for the airline company's meltdown.
“We are past the point where they could say that this is a weather-driven issue,” the transportation secretary said.
The carrier called off about 2,600 more flights by late afternoon Tuesday — and the chaos seemed certain to continue.