Dara Khosrowshahi, who’s served as CEO of Expedia Inc. since 2005 and led the company on an acquisition spree two years ago, officially accepted the Uber CEO post and reports for duty in San Francisco Wednesday.

The Uber board made the official announcement about the hiring of Khosrowshahi on Tuesday night in an email to employees that the company tweeted.

“Dara will be joining us tomorrow, August 30, for an All Hands,” the Uber board wrote. “Add your questions for Dara here, and stay tuned for a calendar invite with more details. He’ll also be meeting with employees around the world in smaller groups over the next few weeks, and spending time with drivers.

“Please join us in welcoming Dara on what promises to be an exciting ride!”

Expedia had no announcement about the move late Tuesday evening on who would replace Khosrowshahi as CEO on an interim or permanent basis. Expedia chairman Barry Diller is the company’s senior executive, and he remains on the job. It is very possible that someone like CFO Mark Okerstrom could be appointed as interim CEO but that is conjecture.

Meanwhile, an Expedia spokesperson confirmed that Khosrowshahi indeed sent an email to Expedia staff — obtained by Recode, among others — expressing his excitement and trepidation about taking the high-profile position at Uber, which is beset with controversies.

“This has been one of the toughest decisions of my life,” Khosrowshahi emailed Expedia staff. “I’ve had the privilege to run Expedia for 12+ years now, and most of you who have been on this journey with me know it has not been easy going.”

He added: “I have to tell you I am scared. I’ve been here at Expedia for so long that I’ve forgotten what life is like outside this place. But the times of greatest learning for me have been when I’ve been through big changes, or taken on new roles — you have to move out of your comfort zone and develop muscles that you didn’t know you had.”

The dramatic turn of events unfolded Sunday night when The New York Times reported that Uber had offered Khosrowshahi the job. Uber had a leadership vacancy because the board forced out founder and CEO Travis Kalanick because of a list of grievances.

Among them, there were allegations Uber tolerated sexual harassment against its female employees; Alphabet’s self-driving car unit Waymo filed a theft of intellectual property lawsuit against Uber’s self-driving car unit; Uber officials allegedly misused the personal medical data of a woman who was rapid by an Uber driver in India, and a federal probe is under way following reports that Uber created a software hack to enable its drivers to play hide and seek with regulators.

And, on Tuesday reports emerged that the U.S. Department of Justice is investigating whether Uber officials violated foreign bribery laws.

It is expected that Expedia will announce on Wednesday who’s currently running the operation in the absence of Khosrowshahi at the globe’s second largest online travel company behind the Priceline Group.

Whoever temporarily or on a permanent basis succeeds Khosrowshahi at Expedia takes the reins of a company that has had some struggles integrating acquisitions over the last year and a half. Khosrowshahi leaves his Expedia post with a lot of unfinished business. 

Expedia needs to quickly show investors it is in capable hands and is stable. The new CEO must help the company regain its momentum in the face of the much-larger Priceline Group continuing to do its thing.

Here’s the full email that the Uber board sent to employees Tuesday night:

Below is an email sent to Uber employees from the company’s Board of Directors this evening:

Team,

We are delighted to announce that Uber’s Board has voted unanimously to appoint Dara Khosrowshahi to be our new CEO.

Dara came to America at nine years old when his family escaped Iran on the eve of the Iranian Revolution. He grew up in Tarrytown, N.Y., trained as an engineer at Brown, and spent many years at IAC serving as Chief Financial Officer and in various operational and strategic roles.

In 2005, he became CEO of Expedia, which he built into one of the world’s leading travel and technology companies, now operating in more than 60 countries. He has four children and not surprisingly loves to travel, one of his favorite trips being to the Angkor Wat temples in Cambodia where his wife Sydney said yes to marrying him.

We’re really fortunate to gain a leader with Dara’s experience, talent and vision. The Board and the Executive Leadership Team are confident that Dara is the best person to lead Uber into the future building world-class products, transforming cities, and adding value to the lives of drivers and riders around the world while continuously improving our culture and making Uber the best place to work.

Dara will be joining us tomorrow, August 30, for an All Hands. Add your questions for Dara here, and stay tuned for a calendar invite with more details. He’ll also be meeting with employees around the world in smaller groups over the next few weeks, and spending time with drivers.

Please join us in welcoming Dara on what promises to be an exciting ride!

-Yasir, Garrett, Matt, Ryan, Arianna, Travis, Wan Ling & David

Here’s Skift’s coverage of the Expedia to Uber Transition for Khosrowshahi Since Sunday Night

Uber’s New CEO Is Expedia CEO Dara Khosrowshahi

Expedia CEO Dara Khosrowshahi to Leave Company With Unfinished Business

Expedia’s New CEO: Who’s Who in Executive Leadership

Expedia CEO Dara Khosrowshahi: Understanding Uber’s New CEO Pick

Can Uber’s New CEO Dara Khosrowshahi Turn It Around Like He Did Expedia?

Photo Credit: Uber Technologies Inc.’s new chief executive officer likely comes with a price tag in the neighborhood of $200 million. Bloomberg