Two billionaires are poised to fly to the edge of space this month, and the sniping is getting worse.

Jeff Bezos’ Blue Origin dismissed Virgin Galactic Holdings’ rocket-powered spacecraft as nothing more than a “high altitude airplane.” The vehicle won’t even break a widely recognized boundary of where space begins when it carries Virgin Galactic founder Richard Branson aloft on Sunday, Blue Origin said Friday in a tweet.

Blue Origin also said its New Shepard rocket will top the so-called Karman Line 62 miles (100 kilometers) above the Earth when Bezos flies on the company’s first crewed mission on July 20.

“From the beginning, New Shepard was designed to fly above the Karman line so none of our astronauts have an asterisk next to their name,” Blue Origin said in the tweet, which included a graphic that took a swipe at everything from the Virgin Galactic vehicle’s impact on the ozone layer to the size of its windows.

The Federation Aeronautique Internationale, which regulates aeronautical sports and record attempts, places the boundary of space at the Karman Line. The U.S. military and National Aeronautics and Space Administration have traditionally used a definition of space as starting 50 miles above the planet. Virgin Galactic’s VSS Unity ship aims to surpass that, with an altitude of about 55 miles.