10 Star Trek Timelines That Were Erased
2. Slingshot Around The Sun For Saturn
Tomorrow Is Yesterday tends to fall between the cracks in Star Trek history. The slingshot-around-the-sun technique was used to great effect in Star Trek IV, though it originates here. The Enterprise is accidentally thrown into the past when it is caught in the gravity of a Black Hole, while en route to Starbase 9. This has the unfortunate side effect of dumping the ship in Earth's atmosphere - in the mid-1960s.
The timeline that is created by the Enterprise's appearance feels like more of a threat than an eventuality. Captain John Christopher has the unlucky honour of being the pilot who spots the ship, only to be beamed aboard. Kirk initially gives him free reign of the vessel, then breaks the news that he can never go home. However, Spock points out that this isn't an option.
Christopher's son manned the first Earth-Saturn mission. Quite annoyingly, said son had yet to be born - so Christopher couldn't remain removed from history.
This remains the only example of using a slingshot around the sun, combined with the transporter, to deposit people plucked from history back into their earlier selves. Technically, the Enterprise manages to prevent a new timeline from being created, though one wonders how Dulmur and Lucsly would interpret it.