I have a small doubt

Memory Alpha wrote:The Akira-class was a class of Federation starship that was in service with Starfleet by the early 2370s

Doesn't that mean it's a TNG era starship? Then why is it in BM3 as the starting ship?

because you have to read the intro at the beginning of the game. you are a soldier from late 24th/ early 25th century, that's why you start in an akira.