A head surely had to roll in the wake of the incredibly stupid decision to fly an Air Force One backup plane and an F-16 Falcon jet fighter over Lower Manhattan last month for a White House photo op.

Friday, one did: The Obama administration accepted the resignation of Louis Caldera, a former secretary of the Army and director of the White House Military Office.

Clearly, Caldera had to go. As government foul-ups go, this one was pretty monumental.

What an accompanying White House report on the incident — which cost taxpayers $357,00 and panicked thousands of New Yorkers haunted by memories of 9/11 — doesn’t make sufficiently clear, though, is whether others should be shown the door, too.

The report, for one, does not explain who came up with the nutty idea for the flyover in the first place.

Nor who was supposed to inform the public — and why that didn’t happen. The Pentagon is undertaking its own review — yet no one, it appears, is looking at the Federal Aviation Administration. Why not?

As director of the White House Military Office, Caldera had ultimate responsibility for keeping everyone at the top in the loop. Yet Deputy White House Chief of Staff Jim Messina says he didn’t learn of the flyover until it had taken place.

Which pretty much explains why Caldera is now out of a job.

But where should the buck stop?

Alas, that remains a mystery.