Other private space ventures, including Blue Origin, funded by Jeff Bezos, Amazon’s chief executive, and SpaceX, founded by the tech entrepreneur Elon Musk, are trying to reduce the costs of getting into space by operating reusable rockets that launch from and land back on Earth. (On Sunday, Blue Origin conducted another successful test of its New Shepard rocket, launching and landing the same rocket for the fourth time.)

Stratolaunch executives said an airborne launcher would have other advantages, like the ability to simply fly to patches of clear sky to avoid foul weather that could scrub a mission. They also say their plane can easily move to areas that are better suited for launching satellites into certain orbits, although the plane needs a landing strip that can handle its great size.

The wingspan of Stratolaunch’s airplane stretches 385 feet. A football field could fit on top of the plane’s wings and there would still be extra room for a few rows of bleachers. The Spruce Goose, the flying boat designed by Howard Hughes that flew only once, has a wingspan of about 320 feet.

There has been tumult around aspects of Stratolaunch.

Its partnerships ended with SpaceX and Orbital ATK. Stratolaunch had worked with them both to develop rockets for blasting satellites into space from the plane. And questions have been raised about whether there would be enough business — given the trend toward smaller satellites — for such a large plane.