David Bailey, born 2241, was a Human Starfleet officer in the 23rd century, who served aboard the USS Enterprise, under the command of Captain James T. Kirk, in the mid-2260s.
Bailey graduated from Starfleet Academy in 2263 and was assigned to the USS Carolina. While aboard the Carolina he served with distinction, earning himself a couple of medals and a promotion to lieutenant junior grade in the process, as well as high recommendations by her commanding officer. By 2265, Bailey was serving aboard the USS Potemkin as navigator. Following the death of the USS Enterprise's navigator, Gary Mitchell, Captain Kirk successfully requested that Bailey be reassigned to the Enterprise to serve as alpha shift navigator. He was teamed with the ship's new helmsman, Hikaru Sulu.
By 2266, Bailey had continued to serve with distinction aboard the Enterprise and, against the advice of CMO Leonard McCoy, Kirk had Bailey promoted to the rank of full lieutenant.
Bailey was the navigator on duty when the Enterprise came to the assistance of the stricken USS Collins. Captain Kirk ordered Bailey and Sulu to coordinate in using the ship's tractor beams and transporters to get all of the Collins escape pods aboard before the Soyuz-class ship suffered a warp core breach.
Bailey was on duty as navigator on stardate 24:09.45, when the ship was hit by a cosmic storm generated by a supernova. A short time later the ship was remotely hijacked by a race of Robots and Bailey along with the rest of the crew were forced to disembark and were taken into custody by the Robots. Bailey was later among the party of Enterprise crewpersons who were able to escape when the robot transporter they were being moved on spontaneously exploded. When the rest of the crew later managed to break free and revolt against their Robot captors Bailey urged Captain Kirk to make an escape with him, however as Kirk pointed out the Robots would soon quell the uprising and it was pointless to resist. Instead Kirk sabotaged the Robot's power unit causing them to shut down and allowing Bailey and the rest of the Enterprise crew to escape.
Later that year the Enterprise established contact with the Fesarius, a vessel of the First Federation. Commander Balok of the Fesarius decided to test whether the Enterprise crew were hostile by threatening to destroy the starship. The pressure of awaiting destruction proved too much for Bailey, and he panicked and started shouting at Captain Kirk and the bridge crew. Relieved of duty, he later returned to the bridge to finish his shift. After the Enterprise had managed to disable Balok's small command ship, Bailey accompanied Captain Kirk and Dr. McCoy to the ship to check on Balok's condition. After a successful first contact was made with Balok, Bailey volunteered to remain behind aboard the Fesarius as part of a cultural exchange.
He remained aboard with Balok for the next two months as Balok finished his patrol, before the Fesarius returned to the First Federation's homeworld. He remained there for over a year before returning to the Federation after Balok's people invited a starship into their sector of space, and led to the beginning of formal diplomatic relationships between the two powers.
By the 2280s, Bailey had returned to the First Federation where he took on an ambassadorial role whilst working with Balok on the Fesarius. In 2286, Bailey temporarily returned to active service and reassignment to the USS Enterprise-A alongside other colleagues from the original Enterprise in assisting Captain Kirk in combating a group of extra-dimensional beings who had been attacking various starships for decades.
In 2373, after a century of exploring the galaxy with Balok, Bailey encountered the USS Voyager in the Delta Quadrant. Though extremely pleased to see other humans again (and to sample replicator cuisine), Bailey rejoined the Fesarius to continue his travels.