'FLAMING LIPS' SINGER Shuts Down OKC Airport ... with a GRENADE!

Question: What kind of dumbass packs a freaking grenade in his carry-on ... and accidentally tries to take it onto a plane? Answer: Flaming Lips singer Wayne Coyne. And he shut down an Oklahoma City airport in the process.

The grenade wasn't live -- thankfully -- but according to the police report, Coyne still accidentally packed it in his bag on November 10th and triggered an alarm at the TSA checkpoint at Will Rogers airport ... like a dumbass.

Needless to say, TSA freaked ... and shut down the terminal while officers frantically tried to figure out how to handle the situation.

nd how's this for hilarious -- according to the police report, the TSA ran around like a chicken with its head cut off ... because it didn't have any "bomb guys" on duty. (Editor's note: isn't that the whole point of TSA?)

According to reports, Coyne was flying to LAX to catch a preview of the new Flaming Lips musical "Yoshimi Battles the Pink Robots" -- and told police he was given the dead grenade at a party as a joke.

Shocker, the grenade reportedly resulted in several missed flights ... and lots of wasted money -- but once TSA determined it was harmless, they let Coyne go.

Coyne tweeted following the incident to make up for the SNAFU, writing, "Sorry Sorry Sorry!! Everyone that was inconvenienced by my grenade at OKC airport."