A Northrop Grumman B-21 bomber has been spotted conducting taxi tests in daylight in Palmdale, California, revealing a first, distant glimpse of the aft section and trailing edge of the Raider.

The start of moving ground tests provides another milestone on the path to a scheduled first flight by year’s end.

Despite the secrecy surrounding the program, the U.S. Air Force allowed Northrop employees to parade the B-21 down a semipublic runway in daylight in Palmdale, and did not hesitate to acknowledge the start of ground testing.

“I can confirm the B-21 is conducting ground taxi activities,” an Air Force spokeswoman said.

The Air Force offered no other details about testing, but the start of ground testing is a sign that first flight could be days or weeks away.

In 1989, the first B-2 aircraft started low-speed taxi tests on July 10. High-speed tests began three days later, and the first flight followed on July 17. Other programs have required weeks or months to clear all taxi testing before a first flight.

But Air Force and Northrop officials are not giving any clues about the pace of planned testing leading to a long-awaited first flight event.

“We’re being a little bit ambiguous because you know in the world of aviation aficionados and journalists wanting to know when first flight is, the adversary does too. So we’re not really giving specifics of how much longer we’ve got,” Tom Jones, president of Northrop’s Aeronautics Systems sector, told Aviation Week last month. “We are on track for a first flight this year.”

The ground testing announcement comes a day before Northrop reports third-quarter earnings.

Northrop started engine runs on the first Raider aircraft last month.

“We’ve made, as a program, investments in a fuel system simulator that we were able to use to derisk fuel transfer, and, as a result of that, we went from fuel-on to integrated test runs in like five days, which is unheard of, particularly in a flying wing type of design where fuel movement is all the more important,” Jones said.

A photograph of the B-21 during an apparent taxi test quickly appeared on Reddit on Oct. 2. Reddit user @Mug_of_Fire seemed to delete the picture within a few hours, however. By then, however, the picture had circulated on several social media sites.

The image showed new details of the trailing edge, aft section and powered-on configuration. The image reveals similar V-shaped exhaust nozzles as the B-2 in both engine nacelles.

The trailing-edge configuration showed at least three moving control surfaces on each wing. It was possible a fourth is installed on the most outboard wing section, but it was not visibly deployed in the picture.