What happened

Shares of space tourism company Virgin Galactic (SPCE -7.41%) declined 5.7% through 11:25 a.m. EDT Monday as the self-imposed May deadline for the company's next test flight of a SpaceShipTwo spaceplane continues to creep closer -- with no news yet of a precise launch date.

So what

Virgin Galactic canceled its planned February spaceflight in February, postponing the resumption of flight testing until May, with little explanation for the delay. Now May has arrived.

Over the past couple weeks, Virgin has conducted two apparently successful test flights of its VMS Eve mothership (the aircraft that carries SpaceShipTwo to altitude before releasing it to blast into space) in preparation for the main event. The last such flight took place nearly a week ago, however, but Virgin still has not stated when it plans to send up SpaceShipTwo.

Little boy wearing a rocket on his back looking out a window expectantly

Image source: Getty Images.

Now what

With the month of May now one-third over, I wouldn't say time is running short, exactly, for Virgin Galactic to keep its promise to resume space test flights. But the absence of an update on the company's timeline is at least a little concerning.

Meanwhile, Virgin Galactic's rivals, Blue Origin and SpaceX, aren't just setting timelines for testing, but they're also preparing to sell tickets for commercial crewed spaceflights, and launching people into space with regularity.

And now it's Virgin Galactic that has to play catch-up -- and that's probably not what its investors were hoping for when they bought into its IPO two years ago.