By Eric M. Johnson

SEATTLE (Reuters) – Richard Branson’s Virgin Orbit on Wednesday released a rocket from the wing of a modified Boeing 747 jetliner in mid-air in a key test of its high-altitude launch system for satellites, the company said.

In the penultimate mission before Virgin Orbit offers commercial satellite launch services, likely before year-end, the 70-foot (21.34 m) LauncherOne rocket cleanly separated from the jetliner.

The rocket, loaded with water and antifreeze to simulate the weight of fuel, was set to crash as planned into the Mojave Desert as the jetliner, nicknamed Cosmic Girl, continued on its flight path.

Virgin Orbit, Firefly and U.S.-New Zealand company Rocket Lab are among companies designing smaller or non-traditional systems to inject smaller satellites into orbit and meet growing demand.

Competition is fierce. Virgin Orbit has fallen slightly behind Rocket Lab, which has already completed six orbital launches, though Virgin Orbit says its rocket can haul about twice the weight.

Branson may also be losing a competitor in Stratolaunch, which had designed a larger aircraft-and-rocket combo system but is shutting operations, Reuters reported in May.

Virgin Orbit also has a significant potential customer. Branson’s Virgin Group has invested in OneWeb’s satellite constellation project which aims to have global broadband coverage in 2021 from about 650 satellites.

Virgin Orbit’s subsidiary VOX Space LLC is selling launches using the same mid-air launch system to the U.S. military, with a first mission slated for early next year.

Virgin Orbit said last month it plans to bring its satellite launch system to Japan in partnership with airline operator ANA Holdings Inc, which will provide maintenance and possibly aircraft.

That launch location will join other sites including the United States, Guam and the United Kingdom, which Virgin Orbit says will provide satellite makers and governments more flexibility.

High-altitude launches, Branson argues, allow satellites to be placed in their intended orbit more efficiently while avoiding some cancellations due to inclement weather on the ground.

Branson’s separate space tourism company, Virgin Galactic, on Tuesday, announced plans for a stock market listing by the end of the year, giving it much-needed funds to take on a rival suborbital tourism service being developed by billionaire Amazon.com Inc founder Jeff Bezos.

(Editing by Cynthia Osterman and Alistair Bell)