The Stratofighter upgrade gives Firehawks the ability to fly into the stratosphere and plunge for the attack. This means the Firehawks can practically teleport to anywhere on the map, even when it's covered by the fog of war, thus allowing surprise attacks without fear of the Firehawks being shot down en route to their target.
Changelog
Tiberium Wars patch 1.05: Firehawks equipped with Stratofighter boosters will no longer fly in stacked on top of each other when groups of Firehawks are ordered to use the ability at the same time.
Global Defense Initiative Third Tiberium War Arsenal 
