On Wednesday, the Transportation Department announced it has launched an investigation into Southwest Airlines’ meltdown that stranded more than a million passengers over the holidays.

The department is also reportedly investigating three unnamed U.S. airlines over whether the companies have been selling tickets for flights they cannot staff — an ongoing scheme recently called out by the CEO of United Airlines.

The developments come after mounting public pressure fueled in part by The Lever’s ongoing reporting on the matter.

In late December, The Lever uncovered documents showing that Democratic lawmakers and state officials from both parties were begging Transportation Secretary Pete Buttigieg to crack down on the airline industry in the months before the Southwest Airlines debacle, in which thousands of flights were canceled largely because the company had failed to upgrade its antiquated computer and scheduling systems.

Buttigieg’s inaction was part of a larger pattern of lax regulation and weak enforcement by the nation’s transportation chief — a former small-city mayor who was chosen for the role not because of his regulatory experience, but because he ran for president.

As the reporting went viral across the Internet, we noted how Buttigieg’s regulatory failures were being systematically ignored by major corporate and liberal media outlets, and weaponized by conservative media and Republican politicians.

We have continued to investigate airlines’ consumer abuses, exploring on our Lever Time podcast how the U.S. airline industry became one of the most concentrated and despised industries in the country, and welcoming longtime progressive lawmaker Peter DeFazio (D-Ore.) onto Lever Live to discuss how the airlines have become increasingly tied to Wall Street.

We also reported on comments made by United Airlines’ CEO accusing his airline industry competitors of selling tickets for flights they could not adequately staff and canceling them at the last minute — an issue that occurred throughout last year, but has only recently been scrutinized by the Transportation Department. And we dug into why D.C. news outlets and Democratic consultants have refused to accept much-needed scrutiny of Buttigieg’s performance as the nation’s top transportation regulator.

To spread the word, we have also produced several videos detailing how federal regulators failed to take action on airline problems, even as airlines have benefited from billions in government support, and tracking how public pressure was finally starting to push Buttigieg and the White House to do their jobs.

Now, finally, the Department of Transportation appears to be taking the airlines’ consumer abuses seriously and preparing to crack down on the industry.

This development illustrates why we do this work: Investigating and reporting on the unscrupulous behaviors of powerful people and corporations can lead to real change.