UnitedHealth Group said on Wednesday a mistake at the hospital was behind the phone call that led to a surgeon being pulled from the operating room to defend a patient's inpatient stay, a move that was eventually criticized by billionaire Bill Ackman.

The hedge fund manager is waging his own money this time in a bid to build another financial behemoth that can rival the life's work of Warren Buffett.

Billionaire investor William Ackman increased his Nike (NYSE:NKE) holdings by 15% and reduced his Chipotle Mexican Grill (NYSE:CMG) shares by 14% in Q4, according to a 13F regulatory filing. Pershing Square

Bill Ackman is the founder and CEO of Pershing Square, a hedge fund with around $12.9 billion in assets under management. On Friday, Feb. 7, Ackman took to social media platform X (formerly Twitter) to reveal that Pershing Square has accumulated 30.

Howard Hughes (NYSE:HHH) shares retreated 8% on Wednesday late morning trading, wiping out Tuesday's 6.8% gain, after confirming a revised takeover proposal from billionaire investor Bill Ackman's Pershing Square Capital Management.

Billionaire investor Bill Ackman's plans to turn real estate company Howard Hughes Holdings into a diversified holding company will not impact how his investment portfolios buy and sell stakes in companies.

Ackman made a bid to take Howard Hughes Holdings private, with the goal of turning the real estate firm into a holding company.

Why: Ackman has for months been pursuing Howard Hughes in a bid to create the next Berkshire Hathaway.Berkshire Hathaway was a textile company when Warren Buffett acquired it in 1965. The legendary investor and his partner Charlie Munger merged two other companies — Diversified Retailing and Blue Chip Stamps — with Berkshire in 1978 and 1983 before closing the textile firm's failing business in 1985.

Billionaire investor William Ackman increased his stake in sportswear company Nike by 15% and cut his investment in fast-casual food chain Chipotle Mexican Grill by 14%, during the fourth quarter, according to a regulatory filing made on Friday.

Recently, billionaire investor Bill Ackman's firm, Pershing Square, disclosed its trades for the fourth quarter of 2024. Among the moves was the continued accumulation of Nike (NYSE: NKE), the sneaker and sporting apparel giant whose fall from grace has caused it to lose over 50% of its peak value since late 2021.

Among other trades, the hedge-fund manager sells a big-name consumer giant and buys into a real estate company.

Uber is an attractive growth investment opportunity in the vehicles and parts sector and recently received backing by Bill Ackman.