2019 had the most CEO departures on record with more than 1,600

• A "staggering" 1,640 CEOs left their posts in 2019, the highest year on record since Challenger, Gray, & Christmas began tracking in 2002.
• It was even higher than 2008, when the U.S. was embroiled in the financial crisis.
• Among them was Boeing CEO Dennis Muilenberg, who was fired in December in the wake of the 737 Max crisis.

Boeing Chief Executive Dennis Muilenburg testifies before a Senate Commerce, Science and Transportation Committee hearing on "aviation safety" and the grounded 737 MAX after two deadly 737 MAX crashes killed 346 people, on Capitol Hill in Washington, October 29, 2019.

Sarah Silbiger | Reuters

2019 was the year of CEO exits.

Thanks to 160 chiefs leaving their posts in December, 2019 totaled 1,640 departures by the heads of U.S. businesses, higher than the 1,484 exits in 2008 when the country was embroiled in the financial crisis, according to Challenger, Gray, & Christmas. The firm started tracking CEO departures in 2002.

"The number of chief executives who announced their departures in 2019 was staggering," Challenger Vice President Andrew Challenger said in a press release.

Perhaps the most notable CEO news in December was the firing of Boeing CEO Dennis Muilenberg. The aircraft-maker has struggled to regain the trust of regulators, customers and the public after two fatal crashes of its bestselling plane, the 737 Max. Chairman David Calhoun will succeed Muilenberg as CEO on Jan. 13.

Tapestry-owned luxury fashion company Kate Spade also announced in December its CEO, Anna Bakst, will not return in 2020. Luggage start-up Away said last month its CEO and co-founder, Stephanie Korey, will step down following reports about an unhealthy company culture.

"Following the #MeToo movement, companies were determined to hold CEOs accountable for lapses in judgement pertaining to professional and personal conduct, creating higher ethical standards at the C-level," said Challenger. "What may have gone unrecognized or was downplayed in the past was not overlooked by boards, shareholders, or the general public in 2019."

Challenger tracks CEO changes at companies that have been in business for at least two years and have at least 10 employees.

The government and nonprofit sector led all industries in CEO turnover in 2019 with 339 exits. The technology sector announced the second-highest number of CEO changes last year, 216, up 42% from 2018.

Demonstrating that companies are increasingly turning to outsiders to replace past CEOs, 784 replacement chief executives came from outside the company and 620 were internal replacements in 2019, the firm said.

— with reporting from CNBC's Nate Rattner.