Viper 8757NC is a Viper Mark VII assigned to the battlestar Galactica (Lay Down Your Burdens, Part I).
A Viper Mark II of the same designation is flown by Kara Thrace during a Combat Air Patrol protecting a Fleet underway replenishment operation. This Viper is the one Thrace is later lost in, crushed by intense atmospheric pressure (Maelstrom). Over two months later, Thrace returns under mysterious circumstances is a remarkably pristine version of this Viper. She claims to have been to Earth and that only a few hours passed for her, but has no recollection of how she got there or how she survived ("Crossroads, Part II", "He That Believeth In Me").