UPDATE, 10:48 AM: I don’t know why AMC didn’t mention this in its release. But it seems that Executive Chairman Charles Dolan exchanged some of his super-vote Class B shares for Class A ones — reducing his family’s voting control to 67% from 71%. BTIG analyst Rich Greenfield discovered this, and he wonders about the timing of the sale: It is taking place before the September 18 trial date in AMC’s $2.5B breach of contract suit against Dish Network, a case that goes back to the satellite company’s 2008 decision to drop the VOOM suite of HD channels. Although Greenfield doesn’t believe the sale reflects lack of faith in AMC’s ability to win the case, the timing “simply looks bad….So why sell $72 mm worth of AMCX right now, with AMCX shares likely to surge if the trial ends up being a positive for AMCX with carriage on DISH resuming?”

PREVIOUS, 7:13 AM: This seems to explain yesterday afternoon’s huge sell off in AMC Networks that resulted in a sudden 4.5% drop in the stock price — the steepest decline in three months. The company’s billionaire Executive Chairman sold 1.75M of his Class A shares “for liquidity and tax planning purposes,” AMC says this morning. We’ll have to wait for his SEC filing to see how much he made from the sale. But it would be at least $72M based on the closing price of $41.16 a share. The news may worry investors who believe that insider trades indicate what people in the know really think about a company’s prospects. AMC shares were -2% shortly after the market opened this morning, but quickly recovered to -0.5%. Dolan’s sale of the Class A shares, which have one vote apiece, affects less than 1% of AMC’s shareholder votes. The Dolan family still controls the Class B shares which have 10 votes apiece, representing 70% of the total voting power. Dolan is also chairman of Cablevision, a director of Madison Square Garden — and may be best known as the man who came up with the concept for HBO.