The 2401 return to service of the restored USS Enterprise-D, flown by Picard's old crew against the Borg on Frontier Day.
Geordi La Forge served as head of the Starfleet Fleet Museum and had spent around twenty years quietly restoring the USS Enterprise-D. The ship had been wrecked on Veridian III in 2371, and La Forge rebuilt it as a personal project.
In 2401 the Borg took control of Starfleet's modern ships during the Frontier Day attack. Because the Enterprise-D was not connected to the fleet's systems, it could not be taken over, and Picard and his former senior officers flew it into battle against the Borg.