WASHINGTON — A secretive California company is gearing up for a test flight of a small launch vehicle it has developed as soon as April 5, according to government notices.

A Federal Aviation Administration Notice to Airmen, or NOTAM published April 3 restricts flight activity in airspace downrange from the Pacific Spaceport Complex-Alaska on Kodiak Island, Alaska, from 4:00 to 10:00 p.m. Eastern (12:00 to 6:00 p.m. local time) April 5. The reason for the restriction is “Due to rocket launch act,” according to the NOTAM, which does not provide additional details.

The NOTAM comes after the FAA’s Office of Commercial Space Transportation issued a commercial launch license to Astra Space. The license, dated March 30 and published on the FAA’s website April 2, authorizes the company to perform a suborbital flight of a vehicle named “Rocket 1” from the Kodiak spaceport. The launch, according to the license, will carry an “inert upper stage without a payload.”

The license offered formal recognition that Astra Space, a company based in Alameda, California, was preparing for a launch from Alaska. However, there were indications last month that the company was the one most likely involved with a launch that Alaska Aerospace Corporation, which operates the spaceport, said was being planned by a “commercial California company” it declined to name.

Alaska Aerospace signed a contract with Astra Space in 2017 to support launches of that company’s vehicle from PSCA, according to the minutes of an Alaska Aerospace board of directors meeting in August 2017. Minutes from a Nov. 2 meeting of the Alaska Aerospace board stated that “Astra is moving forward” with plans, holding weekly planning teleconferences and paying a $100,000 deposit for a launch date. That launch was planned at that time for “possibly February or later.”

Astra Space has kept a low profile, identifying itself as “Stealth Space Company” in some job listings. The company describes itself in those job listings as being “on a mission to provide routine access to earth orbit for the entrepreneurs and enterprises” developing new generations of space systems.

In papers filed with the city of Alameda to lease a building at a former naval air station there, Astra Space described plans to develop a rocket called Astra, 12 meters tall, capable of placing 100 kilograms into low Earth orbit. That vehicle is one of dozens under development by companies and government agencies worldwide, seeking to tap into what they perceive to be the growing demand for dedicated smallsat launch services.