So here is my take on things. The Saber is Aegis's design for a next generation fighter. It says it was not yet accepted in the lore. As of yet the F8A is still not being produced lore-wise or is still prototypes, and is probably competing with the Saber for the bid. The Saber is built for stealth, fast response fighter, while the f8a Lightning is a fleet fighter with heavy armor lots of weapons like its little brother the hornet. Both of these ships are pointed at one thing: Kill the Stinger heavy fighter. Now the leaked Lightning was bigger than the Saber, but might be reduced in size, this would cause the Saber to maybe be a heavy fighter instead of a medium fighter. After the fall of Messer, Aegis has not done well and is trying to sway public opinion, hence releasing the prototype Saber to the public to hype them about Aegis. Anvil still has their hand hidden and the public does not know about it. We know the F8A is accepted as the newest main fleet fighter for the UEE Navy and this is probably because they want a brawler to confront the stinger not a stealthy fast mover.
TLDR; Saber competes against Lightning for Navy bid, and loses. Saber leftover stock is sold to civilians.
