Good news, United Continental Holdings (UAL 4.98%) investors: Your company's 787 fleet may be back in the air next month. The carrier has penciled in May 31 for its first domestic flight of the jetliner since January.

Why the confidence? Earlier this week, Boeing (BA 0.39%) stock rallied on news that the company has completed its final flight test of a new battery that appears to include changes publicly suggested by Tesla Motors (TSLA -3.40%) chief Elon Musk. Ironic given how Boeing rebuffed Musk's offer to help with a redesign. United is the first U.S. carrier to take delivery of the 787.

Regulators still have to approve the battery system, which could come within weeks. There's also expected to be a certification period before United or any other carrier is permitted to fly the 787 on certain long-haul routes.

Even so, the test has to be welcome news for owners of Boeing stock, says Motley Fool contributor Tim Beyers in the following interview with The Motley Fool's Erin Miller. At the very least, Tim says, efforts to fulfill backlogged orders should begin anew.

Does this news make you more bullish on Boeing's prospects? What about United's? Please watch this short video to get the full takeaway, and then leave a comment to let us know whether you'd buy or sell Boeing stock now, and why.