Flares
Used to try to spoof infra red guided missiles, they tend to use a lot of them as they are relatively cheap compared to the plane. The idea is to swamp the heat signature of the plane with that of the flares and confuse the hell out of any missiles fired at the plane.
The problem is that they are difficult to detect so you can use the countermeasure, at least with radar guided you can detect the radar signal.
