There were planned extensions of the Saturn City Subway, but were never implemented due to time constraints.
There was a planned extension of the Main Line to connect with the Shekel Line. Under the original plan, the Shekel Line was to have connected with the Main Line via a connection that allowed trains from both directions to connect, forming a loop. However it never was implemented due to time constraints.
Under the original plan, the Shekel Line was to have four tracks for local and express services, between Leafshire Road and Jupier Avenue and Shekel Avenue and Concourse Avenue. The express service was to run at all times, and there was even a designation (<4>) for the proposed express service. The proposed plan was to have space for express tracks, with the express tracks ending at what is now 150th Street–Saturn City University and Lexington Place stations, which were to be express stations. However, it was ultimately decided that the line would have only two tracks, and so opened that way.