The US Transportation Department would investigate Southwest Airlines over a large number of canceled and delayed flights to determine if the airline had control over the situation.
On Monday, Southwest canceled 2,886 flights, or 70 percent of scheduled flights, after canceling 48 percent a day before.
It also canceled 60 percent, or more than 2,400, of its Tuesday flights.
The department said the rate of cancellations and delays are disproportionate and unacceptable.
It added that it is also concerned by Southwest Airlines’ failure to properly support customers after the cancellations and delays.
The deparment vowed to "closely examine whether cancellations were controllable and whether Southwest is complying with its customer service plan as well as all other pertinent DOT rules."
