6 Oldest CEOs in America in 2015

Sumner Redstone holds three titles: chairman of both Viacom and CBS and, at age 92, nonagenarian. The combination has caused investor concern over whether Redstone can remain in charge. Shares are down roughly 39% since the beginning of 2015.

Los Angeles County Superior Court Judge Clifford Klein recently ruled there’s no need for an additional immediate evaluation as Redstone’s former girlfriend Manuela Herzer requested in a lawsuit seeking to have the executive declared mentally incompetent. Redstone’s camp says he has taken and passed mental competency tests.

As Americans’ life expectancy continues to rise, similar dramas are playing out at other companies. Earlier this year, now-88-year-old Tom Benson, owner of the New Orleans Saints football and Pelicans basketball teams, successfully deflected a competency lawsuit. Last year Donald Sterling, 81, wasn’t so lucky when it came to the sale of the Los Angeles Clippers basketball team.

At most public companies, operational leadership is the responsibility of the CEO, not the chairman. A small number of companies set a mandatory retirement age for CEOs. According to information from The Conference Board, 21% of businesses with annual revenue of $10 billion or more have such policies, almost always setting top age at 65. But most companies do not set limits, as “it would make no business sense for a company to distance itself from” older talent, says Conference Board Managing Director of Corporate Leadership Matteo Tonello.

The average age of a CEO of S&P 500 companies rose by 3% between 2004 and 2014 to 56.9 today, according to Spencer Stuart. That tracks closely with a Fortune analysis conducted in early December of the current Fortune 500 CEOs that showed the average age of a Fortune 500 CEO as 57.

But there are some notable exceptions.

Here are the six oldest CEOs of Fortune 500 giants, as of early December.