It’s not a common occurrence, but that makes it no less scary. Transportation Security Administration agents used an X-ray machine to find a handgun Wednesday in a departing Honolulu passenger’s carry-on. It was the first case this year, following one last year, and there was no ammunition with it.

Still, it only takes one firearm brought aboard a plane to enable a terroristic act. And given the advent of plastic printed “ghost guns” — harder but still possible to detect — it’s a legitimate cause for worry.