Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Orbitz Worldwide (UNKNOWN:OWW.DL) were losing altitude today, falling as much as 13% after a major investor sold part of its stake in the online travel merchant.

So what: PAR Capital Management dumped 8.1 million of the 24.6 million shares it held, a decision which Paul Reeder, president of the investment group, said was to "better diversify our portfolio." Reeder stood by Orbtiz, saying that he was "optimistic" about the company's future, especially growth in the hotels sector. Orbitz shares jumped by more than a third last week after a blowout earnings report led by strong performance in its hotel segment.

Now what: I wouldn't get too worked up about today's drop or PAR's sale, since the investment fund is holding on to more than two-thirds of its holdings in the stock. Selling nearly 10% of shares outstanding will naturally depress the share price, but after the run Orbitz has been on lately, still up about 300% after today's tumble, it's easy to see why PAR would want to "diversify." I'd be more concerned about Orbitz's valuation after such a spike in share price, as earnings have not kept pace. With a forward P/E of 27, the travel dealer has high expectations to live up to.