When we swing a fly swatter at a fly, the speed of the swatter is one of the main reasons the fly struggles to escape. Fly swatters can be swung at speeds that exceed the typical flight speeds of common houseflies. Houseflies usually fly at speeds around 4.5 miles per hour (7.2 kilometers per hour), while a quick human swing can easily surpass this. The sudden acceleration and high velocity of the swatter make it difficult for the fly to react in time and adjust its flight path to avoid the impending danger.

Despite having compound eyes that provide a wide field of vision, flies face challenges in perceiving the approaching fly swatter accurately. Compound eyes are made up of thousands of tiny lenses, called ommatidia, which are excellent at detecting movement but not as good at determining the distance and size of objects precisely. When the fly swatter moves towards the fly rapidly, the fly may detect the motion but misjudge the distance, thinking it's farther away or closer than it actually is. This misperception can lead to poor decision - making about when and which direction to fly to evade the swatter.