Project Swing By was a Federation exploratory project carried out by California-class starships which aimed to check in on planets previously visited by Starfleet.
Following a visit to the Betans of Beta III in 2380, who had once again fallen under the control of Landru, Captain Carol Freeman of the USS Cerritos explained to her first officer, Commander Jack Ransom, that she felt "Nothing against second contact missions, but the Cerritos should be popping in on those legacy civilizations before they unravel." Ransom agreed, but noted that "'popping in' is against regulation. We would need specific orders." She further opined, "I just hate seeing a perfectly good society get destroyed by a Gamester of Triskelion or whatever, because Starfleet has a policy of some intervention." (TOS: "The Return of the Archons"; LD: "No Small Parts")
After years of lobbying Starfleet for the project by Freeman, it was finally accepted in 2381 by Vice Admiral Les Buenamigo. The Cerritos' first Swing By mission was to check in on the Ornarans and the Brekkians, two species that were originally contacted by the USS Enterprise-D seventeen years earlier. The results were mixed; the Ornarans were found to have experienced a difficult withdrawal period, but had already recovered and required no further Starfleet assistance. On the other hand, the Brekkians were found to have suffered a previously (ostensibly) undetected Breen incursion, which was subsequently resisted by the timely arrival of the newly-unveiled Texas-class USS Aledo. Despite the mission's difficulties, Commander Ransom suggested to Captain Freeman that the mission was so unexpectedly productive that overall "everyone's gonna be very impressed."
Ransom was wrong; Starfleet Command deemed the initiative a failure due to the disastrous Breen encounter and a subsequent PR disaster resulting from Freeman mishandling the presence of FNN journalist Victoria Nuzé on the Cerritos, and chose to decommission the entire California-class. However, it later came to light that Buenamigo had prior knowledge of the Breen incursion that he had deliberately withheld in order to sabotage Project Swing By and "force" his pet project to come to the rescue, and the decommissioning was rescinded after all three Texas-class vessels were destroyed due to faulty artificial intelligence causing them to go on a rampage. (TNG: "Symbiosis"; LD: "Trusted Sources", "The Stars At Night")