they don't and that is why the saying "yea, when pigs fly" is so popular. the saying points out that the likely hood of them doing whatever was said is equal to that of pigs flying. basically saying "yea, that's not going to happen" in a fun way. hope this helped :)
Pigs do not and can not fly. If someone says that will happen when pigs fly
they are stating it will never happen. The saying is used as humor.
More often they fly because of a huge amount of energy takes them from a sedate station well into two gees of force and air is found between them and the ground.
This flight of the pigs is a direct result of damned good "Trebuchets".
Because the Swine Flu
Pigs?... Oh...... yea ! their body parts fly when they blow themselves up for Allah.
