It is said that all ships by the time of Victory have Minovsky Craft Systems that allow them to fly in atmosphere. However, the only time I recall the
Reinforce leaving Earths atmosphere, in episode 16, it was towed up by a
Salamis Kai fitted with a booster. Since the
Reinforce is said to be an older ship that wasn't still in use, perhaps it wasn't equipped with the system, like the active duty
Salamis Kai (And other older EFSF ships shown flying later on).
For what it's worth, later in the series the
White Ark requires a booster even though it has the MCS, but I'd chalk that up to it's small size, and the
Reinforce Junior is shown without one, but it isn't clearly shown flying back into space, so it's hard to say one way or another.
