Harford was appointed COO in January last year, while Messina, Uber's first-ever chief marketing officer, also joined the company last year.
"I now have the ability to be even more involved in the day-to-day operations of our biggest businesses, the core platform of Rides and Eats, and have decided they should report directly to me", Khosrowshahi said in his message to employees.
In an internal memo, chief executive Dara Khosrowshahi explained the moves were meant to give him more control over day-to-day operations. "Given that we're a month past the IPO, now is one of those times, and I've been discussing this topic a lot with Barney and the leadership team", TechCrunch quotes Khosrowshahi as writing in the email.
Mac, one amongst our most tenured and talented leaders, will exhaust on the Global Rides business, reporting to me.
Finally, it's increasingly clear that it's crucial for us to have a consistent, unified narrative to consumers, partners, the press, and policymakers.
In a letter to Uber staff on Friday, Mr Harford thanked employees and outlined a few of the company's signature accomplishments. Uber did not immediately return a request for comment. "It's been an honor".
FedEx Express Drops Amazon, Focuses On 'Broader E-Commerce Market'
It's also launching a program that lets contractors start businesses delivering packages in vans bearing the Amazon smile logo. According to Reuters , FedEx plans to hire 700 part-time Express drivers in 160 rural and residential markets.
Two of Uber's top executives were pushed aside last week in a management shake-up at the ride-share company following its lackluster initial public offering.
Uber then posted a $1bn (£790m) loss last month, despite strong revenue growth. The stock closed Friday below the IPO price of $45 a share. Shares have fallen by almost 2% since pricing at $45.
Now we own made so powerful progress over the leisure two years, and Uber is in a magnificent better location every internally and externally. Harford vowed to undergo sensitivity training.
Uber spokesman Noah Edwardsen said that Harford's departure was unrelated to the investigation, which has since concluded.
Messina's tenure at Uber lasted just nine months. Khosrowshahi announced Jill Hazelbaker, the company's senior vice president of policy and communications, was promoted.
On condition that Advertising is so most well-known to our business, and our label continues to be challenged, I own furthermore chose to unify all marketers across Efficiency, Product, Rides, Eats, Security, ATG, Freight, Nemo, and Employer Stamp globally below Jill.