Answer: The are formed in a way so they create less friction against the air and water. Helping the jet stream create less traction so it moves faster. Like how a bullet is designed. The pointed front and narrow body helps it move faster through the air. Less things sticking of these object so friction is avoided, and they can easily move speedily. The same thing goes for cars, the more narrow they are as well as pointed makes it easier to push through the air making the wind resistance extremely low.
Hope this helps :)
