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 aircraft financing company AerCap Holdings N.V. (AER 2.04%) jumped 12% in late trading after rumors emerged about an acquisition.

So what: Bloomberg is reporting that AIG (AIG -0.04%) is in talks to sell its jet-leasing finance business to AerCap Holdings. The unit was supposed to be sold to Chinese buyers, but AIG hasn't been able to close the deal. AerCap may need to bring in other partners to complete it. 

Now what: The AerCap acquisition is still only a rumor, and it's dangerous to buy on such rumors. AIG may also pursue an IPO, so it isn't as though AerCap is going to get a fire-sale price. I'd wait to see how this plays out, but I'm certainly not buying on the rumor today, because those gains can evaporate tomorrow if the deal doesn't turn out to be real.