The stunt worked because gyrocopters and other ultralights are extremely difficult to pick up on most radar systems. They’re small, fly at low altitude and at low speeds.

They’re also relatively cheap and often much quieter than other aircraft. It’s their very simplicity that makes it hard for high-tech detection systems to track them.

In recent years, that’s made ultralight aircraft a favorite of Mexican cartels for smuggling illicit drug shipments across the southwestern border. The aircraft, some of them homemade contraptions — such as the one depicted above — have vexed both federal and local authorities in the border states.

Government agencies have spent millions of dollars putting systems in place to track smugglers using these aircraft. But there hasn’t been a lot of thought about their use for potential attacks.

So how worried should we be?

On Feb. 18, 2010, software consultant Andrew Joseph Stack flew a single-engine Piper Dakota into an Internal Revenue Service office in Austin, Texas. Two people died — Stack and 68-year-old IRS employee Vernon Hunter. Though tragic, the attack was far from catastrophic.

If an ultralight such as a gyrocopter — a much smaller and lighter aircraft — were to hit the Capitol building or the White House, it would likely bounce off. Such an attempt might wind up killing or injuring the pilot — and maybe cause a slight repair bill on the targeted property.

But some commentators have suggested that Hughes could have been carrying weapons or bombs.

The idea of a terrorist strapped in a suicide vest, suddenly dropping out of the sky is indeed frightening. There are a lot of ways these aircraft could spread chaos and do some damage.

But dropping from the sky also draws a lot of attention. Even though police didn’t shoot Hughes, they easily could have. “Had it gotten any closer to the speaker’s balcony they have long guns to take it down,” Rep. Michael McCaul, chairman of the House Homeland Security Committee, said.

There’s a reason bombers more often than not use cars and trucks — because they’re a lot more subtle, practical and dangerous.

On April 19, 1995, Timothy McVeigh blew up a rental truck packed with ammonium nitrate in Oklahoma City. He killed 168 people and injured more than 680 in the second-deadliest terrorist attack in U.S. history.

It’s true that we need to think creatively about threats. If 9/11 taught us anything, it’s that terrorists can be very creative. We shouldn’t allow ourselves to rule out the ridiculous or the insane.

Since then, Congress has spent countless dollars on homeland defense. We’ve outfitted law enforcement with a staggering amount of military hardware. The federal government created a massive domestic surveillance network.

But there are still things we don’t understand and things we can’t predict … and there always will be. You can’t be 100 percent on guard all of the time.

We can’t let fear of the highly unlikely dictate national policy and the way we live our lives. Unless you want to shoot a mailman in a flying bicycle.