Transportation Secretary Elaine Chao resigns following insurrection at US Capitol | Dump Trucks Charlotte NC

It has been the honor of a lifetime to serve the U.S. Department of Transportation. pic.twitter.com/rFxPsBoh6t

— Sec. Elaine Chao (@SecElaineChao) January 7, 2021

Chao's resignation will leave the DOT without a permanent secretary starting Monday. According to agency process, if the secretary leaves office, the deputy secretary is next in the line of succession. That permanent position is currently vacant; DOT General Counsel Steven Bradbury performs the functions and duties of the deputy secretary. 

Chao said in a statement she would help President-elect Joe Biden's DOT secretary pick, Pete Buttigieg, assume the role. Buttigieg still needs Senate confirmation, but the newly won Democratic majority paves an easier path — one that could be traversed this month. The last time the presidential administration changed from Republican to Democratic, in 2009, Ray LaHood was confirmed as DOT Secretary two days after inauguration.

Under Chao, the DOT prioritized deregulation and collaboration with private entities.

"She has been a champion of infrastructure and transportation safety, effectively leading the department over the last four years," Rep. Sam Graves, a Republican from Missouri and ranking member of the Committee on Transportation and Infrastructure, said of Chao in a statement.

Chao was the first Cabinet member to resign, although other high-ranking officials in the Trump administration have also done so following the insurrection Wednesday, including Secretary of Education Betsy DeVos late Thursday night. DeVos cited the same reasons as Chao for tendering her resignation, less than two weeks before Biden is to be installed as president. 

Chao's tenure at the Transportation Department was marked by a bruising critique of how her agency handled grounding Boeing’s 737 MAX planes as well concerns about her potential conflicts of interest and abandonment of Trump's multitrillion-dollar infrastructure plan, according to Politico. 

But she took pride, according to Politico, in her department's prioritizing of rural projects, as well as its sparring matches over California's high-speed rail project and the Gateway Program to replace aging rail and transit tunnels in New York and New Jersey.

Chao, who is married to Senate Majority Leader Mitch McConnell, also was labor secretary under President George W. Bush, serving during his two terms.

Jean Dimeo added to this report.