Multiple realities
(covers information from several alternate timelines)

The air tram was a Federation passenger transport that was in service with Starfleet in the late 23rd century. These trams were used for transporting Starfleet personnel between air tram stations. The air tram was compartmentalized into a passenger cabin and a cockpit.

Admiral James T. Kirk was transported to Starfleet Headquarters in San Francisco aboard air tram 3 in the 2270s. Upon landing, the admiral met with Commander Sonak and proceeded to a meeting with Admiral Nogura. (Star Trek: The Motion Picture)

Air trams were still in use in San Francisco in an alternate 2372. (VOY: "Non Sequitur")

Air trams (or vehicles that resembled them) were also common on Farius Prime in 2374. (DS9: "Honor Among Thieves")

Commissioned ships

In the shooting script for Star Trek: The Motion Picture, an airtram was defined as "an anti-gravitional train flying several feet above the ground".
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