What: Shares of military drone maker Aerovironment, (AVAV -0.12%) lost 13.4% of its value in January, partly due to insider selling.

So what: The month didn't start well for Aerovironment after CEO Timothy Conver announced a 10b5-1 trading plan to sell up to 320,000 shares of company stock over the next nine months. These are trading plans executives put in place to sell stock without the insider controlling the timing of sales. 

What's strange about this move is that Aerovironment hasn't yet started to see fruit from investments it's making in next-generation military drones, and new commercial drones. Maybe those investments aren't all they're cracked up to be.

Now what: Aerovironment is one of the few ways investors can invest in the coming drone revolution, but it's yet to turn that into significant revenue or profits. Management is hoping the next five years see a surge in growth, but most new products are just in the testing phase today. That's why the CEO selling shares can be a big deal for traders worried about future growth. More important will be the company's next quarterly report, and comments about future growth. Insider sales should be seen as a data point, but I would worry more about fundamentals when it comes to the future of drones.