What happened

Small drone aircraft-maker AeroVironment (NASDAQ:AVAV) entered into September on a high note -- then promptly fell asleep. Reporting earnings on August 30, 2017, AeroVironment boasted of strong, 21% sales growth. Although the company lost money in the quarter, it lost far less than it had guided investors to expect, sparking an 18% rally in the stock and setting up AeroVironment for a great September to follow.

Instead, AeroVironment basically tread water for the next two weeks before finally showing signs of life again in mid-September. A couple of positive news items later, the stock ended up gaining a respectable 10.4% for the month.

So what

There were two things that brought AeroVironment stock back to life mid-month. First, on September 19, AeroVironment announced that its small "efficient energy systems" division -- which builds electric power-charging equipment for vehicles -- had been chosen to serve "as an official North American provider of BMW and MINI-branded TurboCord accessory EV chargers." With this announcement, AeroVironment says it is now "a preferred integrated North American home charging solution supplier" for nine of the world's biggest automakers.

The stock gained 5% on the day this news was announced. It proceeded to rise from there through the tail end of the month, including enjoying a modest rise in price upon the announcement that the U.S. Army had placed a small order for additional Switchblade UAVs on September 27.

Man on scooter driving up a red arrow

Despite little news in September, AV stock just kept motoring higher. Image source: Getty Images.

Now what

Sadly, October isn't looking as propitious for AeroVironment. Although the stock initially rose as October began, its ascent appears to have stalled. Today, for example, AeroVironment stock is down 2.8%.

Why? Your guess is as good as mine, as there's no news of note to clearly explain the decline. That said, with AeroVironment stock up more than 120% over the past year already, it could simply be the case that investors are starting to think the stock's valuation is a bit stretched. Even with analysts forecasting strong, 27.5% annual earnings growth for the company, at 63 times earnings, AeroVironment stock is looking priced to sell.

Rich Smith has no position in any of the stocks mentioned. The Motley Fool recommends AeroVironment. The Motley Fool has a disclosure policy.