An extremely compelling unidentified flying object incident occurred over Washington, D.C., in 1952. Did another UFO pay a visit to D.C. on Tuesday?

Probably not, but it's a possibility — seriously.

First, the facts. An intruding radar contact entered the national capital region air defense area at about 8:30 a.m. on Tuesday. The contact was taken very seriously. The White House and Capitol were locked down, and both fighter jets and a helicopter were scrambled to investigate. NORAD first identified the contact as a "plane," then deleted the associated tweet. Authorities now say the alert was a false alarm. But what was the contact?

Capitol Police told CNN that the "big, slow-moving blob of something" might have been birds. Gary Andrews, president of a leading bird-detection radar manufacturer, Detect Inc., told me that birds might indeed have been the culprit because "the government radars may not have bird suppression algorithms." He pointed to a recent bird-related false alarm in South Korea. Alternatively, WTOP's national security correspondent said it might have been a Mylar balloon. But Fox News reported government sources saying the contact was "hovering," at least temporarily.

An anomaly is unlikely considering the contact's sustained track. But, and not just because of the hovering report, I'm unconvinced that this was birds or a balloon.

First off, the capital air defense area is the nation's most tightly monitored region. The contact entered at least the 30-mile outer ring of the air defense area. That's about all we know. NORAD referenced "operational security" concerns to ignore my questions as to the contact's origin, speed, track path, dissipation/loss-of-track point, and whether it hovered. But the lockdown suggests the contact either entered the capital air defense area's 15-mile inner ring, or got close to it.

Now consider a little something named Sentinel.

Sentinel is the Army radar system deployed to protect the government's inner sanctum: the White House, Congress, and the Pentagon. Upgraded in recent years to include tracking of small ground-launched munitions, the platform is world-leading. Sentinel utilizes an extremely advanced X-band radar system, predisposed to discriminating individual birds, balloons, and weather from planes or drones. Birds fly in and out of the D.C. air defense area all-day, everyday, but Tuesday's alert was very rare. I cannot find a similar incident since someone decided to fly a gyrocopter up to the Capitol complex in 2015.

The rarity speaks to a key point: The radar operators utilizing Sentinel and other platforms are very good at discriminating birds (geese flocks are always flying in Washington's airspace) and balloons, and separating radar contact merges (where a group of contacts appear as one). Tuesday's contact obviously concerned commanders enough that they launched multiple interceptor aircraft and the Secret Service locked down the White House. Was that because the track showed apparent purpose in flight toward critical facilities?

Yes, perhaps it was birds or a balloon. But if not, what was it?

Well, ponder this. We do know that intelligently operated machine-based UFOs, not belonging to the U.S., China, or Russia, are now being tracked globally. These invisibility-capable UFOs can travel at hypersonic speeds in the air and hundreds of knots underwater, and often show a special interest in sensitive government facilities (an interest that is increasingly being reciprocated). And yes, they can hover!

Makes you wonder what that might have been on Tuesday, doesn't it? Was it birds or something extraterrestrial?