You may have looked up at the sky a few minutes ago and thought: Okay, that one wasn’t a helicopter.

And you were right. The loud sound heard overhead around D.C. shortly after 11 a.m. was a flyover from some fighter jets, part of the dedication of the new National World War I Memorial in D.C.

TOMORROW, Fri. April 16, 10am EDT / 7am PDT TUNE IN: https://t.co/2SGwNUk1gw for historic FLYOVER by 94th Fighter Squadron as they salute all who served in #WW1 & new National #WWI Memorial DC. AKA 94th Aero Squadron, was most victorious air warfare unit of #WWI. pic.twitter.com/O2BRSCXGMy

— WW1 Centennial – Doughboy Foundation (@WW1CC) April 15, 2021

The jets were part of a live broadcast ceremony meant to commemorate the sacrifices of the “4.7 million Americans [who] sent their sons and daughters off to fight a war that would change the world,” according to a press release from the World War I Centennial Commission. Besides the flyover, officials also unveiled an American flag first flown in D.C. on April 6, 2017, the centennial of the United States’ entrance into World War I. Since then, the flag has been on tour, flying over American battlefield cemeteries in Europe. It will now be a permanent fixture at the World War I memorial on the National Mall. 

The flyover was close to the White House, where the daily press briefing was, for once, drowned out.

Yeah that flyover was real loud in the video of the WH press briefing. The two jets were just blocks away at the new WWI monument dedication. https://t.co/2etumJzqnw pic.twitter.com/ekUyAT6Rev

— Jordan Pascale🎙️ #WeMakeWAMU (@JWPascale) April 16, 2021

Beyond the White House, the noise seemed to startle plenty of folks in neighborhoods all over town.

https://twitter.com/thegoodcarmah/status/1383075398389489667

Some suggested the ceremony was poorly publicized, and the loud noise merited an emergency alert from the city.

I’d be pro-D.C. using the emergency alert system to tell residents about this ahead of time, so the timeline doesn’t briefly think Red Dawn has happened https://t.co/j6G4YOm4Fz

— Zach Montellaro (@ZachMontellaro) April 16, 2021

If the noise was frightening for you, you are not alone.

As a person with PTSD, this was… not a great experience. I’m gonna go throw up again now, and hopefully the feeling will return to my extremities. https://t.co/2G8Nig0xEY

— farrah skeiky (@reallyfarrah) April 16, 2021

This post has been updated with additional context about the flyover.