This is significant because the maneuvers were ordered either by,  “The highest echelons of the District of Columbia National Guard,” (NY Times) or directly ordered by Donald Trump. (AP)

So, the military has ordered an investigation, and the implication is that the crew, and people above them in the chain of command, may be facing jeopardy as a result of following orders.

Clearly, this is a push-back against Donald Trump and Evil Minions^™, which can be taken two ways:

• It is reassuring because it means that the military has remained largely unaffected by the politicization of the government under Trump.
• It is concerning because it indicates a level of push-back to civilian authority that might presage a coup.

Actually, both could be correct:

The National Guard helicopter crew that flew low over protesters in the nation’s capital this week has been grounded, the Army secretary told reporters Friday.

The Army initiated an administrative investigation, called a 15-6, after a UH-72 Lakota was seen making low maneuvers in Washington, D.C., on Monday, Army Secretary Ryan McCarthy said. The crew was grounded immediately after the investigation began, he added.

………

Videos showed Lakota and UH-60 Black Hawk helicopters kicking up debris as officials tried to force demonstrators who’d broken the city’s 7 p.m. curfew off the streets. The Black Hawks were reportedly operated by the FBI.

McCarthy declined to say who ordered the helicopter crews to fly low over the protesters in Washington, citing concerns that he’s in the chain of command and the investigation remains ongoing.