What happened

Virgin Galactic Holdings (SPCE -0.57%) came into May with a self-imposed deadline to restart its testing program before month's end. The test happened, and it helped propel the shares 41% higher for the month, according to data provided by S&P Global Market Intelligence.

So what

Virgin Galactic came into the month on a bit of a losing streak. The space tourism start-up is behind schedule, missing its original goal to begin commercial operations last year. And its testing program has faced setbacks that left its timetable uncertain.

The Virgin Unity spacecraft gliding in for a landing.

The Virgin Unity spacecraft. Image source: Virgin Galactic.

The company earlier this year said it hoped to get back on track in May, though that goal was thrown into doubt early in the month after management warned it was evaluating a new issue that it said could further delay testing. Fortunately, that issue was not as bad as initially feared.

On May 22, Virgin Galactic returned to space with a successful test flight. A number of analyst upgrades followed soon after. The stock took flight along with the company's Unity spacecraft. While up 41% for the month, Virgin Galactic shares actually nearly doubled in value from May 12 through month's end.

Now what

The good news is that Virgin Galactic operations have resumed. The bad news: We still don't know for sure when passenger service might begin. Space is full of complications, and Virgin Galactic still has a lot to prove in the months to come if it is to become the growth stock investors hope for.

But coming into May, there was reason to worry that Virgin Galactic might never get airborne. The testing regime was flailing, and new competition is on the horizon. While Virgin Galactic remains a speculative endeavor, the successful launch reassured investors that the company remains on course. That was enough to get the stock soaring in May.