Flechettes were used as an air-dropped weapon in World War I. These were about four inches long and weighed a couple of ounces. Dropped from an airplane over enemy trenches, these gravity missles were capable of penetrating a helmet and the wearer's skull.
Modern day flechettes are used in special artillery shells called "beehive" rounds and intended for use against troops in the open. There are also flechette rounds for the M203 grenade launcher and the 12-gauge shotgun.
In the 1960s the U.S. Army began early developmental work on a flechette rifle cartridge. It was never fielded.