NEW YORK (CNN/Money) - Companies announced 23 percent more chief executive departures in November than the month before, and more than two-and-a-half times as many as in November 2004, global outplacement firm Challenger, Gray & Christmas said Tuesday .

The November number of 118 marks the eighth time this year that monthly CEO departures totaled more than 100, the report said. There were 96 in October and just 46 in November 2004.

Overall, CEO departures have doubled in 2005, according to the Challenger survey, with 1,228 departures recorded from the beginning of 2005 through November, up 102 percent from the same period in 2004.

The average age of departing CEOs was 59.9 in November, the highest age since September 2004, the survey said.

Among the month's more notable departures was Daniel Lynch, chief executive of Imclone Systems (up $0.35 to $32.69, Research), the company most famous for its ties to the insider trading scandal that led to the imprisonment of Martha Stewart.

The outgoing CEO had been in place since April 2003, after taking over for Harlan Waksal, the brother of former CEO and Imclone founder Sam Waksal, who is now serving seven years in prison for insider trading.

Kieran Burke, chief executive officer of Six Flags Inc. (down $0.06 to $7.19, Research), was another high-profile departure in this month's report.

Burke was on the losing side of a power struggle with the company's largest stockholder, Daniel Snyder, owner of the Washington Redskins, in a boardroom battle that also claimed two directors, one of whom was the company's chief financial officer.

And in another power play, Amtrak CEO David Gunn was ousted for his opposition to ending federal subsidies that keep the struggling transportation giant operating.

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