In the high Mojave Desert, the airframe of Paul Allen's giant, mysterious plane for carrying rockets into space is approaching completion.

It has twin fuselages, 95 feet apart, that are joined across the top by a massive wing, 385 feet from tip to tip — longer than a football field including the end zones.

With a larger wingspan than any aircraft ever built, the six-engined plane — officially called Stratolaunch — has been nicknamed the Roc, after a mythical Middle Eastern bird so big it could carry an elephant in its claws.