When ejected from an aircraft, chaff forms the electromagnetic equivalent of a visual smoke screen that temporarily hides the aircraft from radar.
Chaff also serves to decoy radar allowing aircraft to maneuver or egress from the area.
It consists of small, extremely tie fibers of aluminum or aluminum-coated glass that disperse widely in the air when ejected from the aircraft and effectively reflect radar signals in various bands, in order to create a very large image of reflected signals ([base "]return[per thou]) on the radar screen.
In the air, the initial burst from a chaff bundle forms a sphere that shows up on radar screens as an electronic cloud.
The aircraft is obscured by the cloud, which confuses enemy radar. Since chaff can obstruct radar, its use is coordinated with the Federal Aviation Administration (FAA).