If the majority of the models in a unit armed with missile weapons have this special rule, the unit may declare that it will 'Fire & Flee' as a charge reaction:

Fire & Flee

The unit launches a volley of weapons fire before turning to flee from the enemy. If a unit with this special rule is armed with missile weapons and can draw a line of sight to the charging unit, it may declare that it will Fire & Flee. The unit will Stand & Shoot before turning tail and fleeing from the charge. However, due to the time spent shooting at the charging foe, when making its Flee roll the unit rolls two D6 and discards the lowest result. If both dice roll the same result, discard either.

Note that, if the distance between this unit and the charging unit is less than the Movement characteristic of the charging unit, this unit must either Hold or Flee.