1: Underground spaceships discovered. The ships were built underground, and there are supporting facilities for the spaceships. Hangars, spare parts, etc. Group is a GoI from RCPA that was defeated.
2: Authority attempts to contact group that makes the spaceships, but relations between the 2 groups break down mainly due to the group's unwillingness to let the Authority reverse-engineer their tech in order to not repeat history (aka becoming batshit crazy).
3: A greater threat shows up. This "greater threat" is to be the RCPA.
4: Authority steals a spaceship and reverse-engineered it during the cooperation. That advances the Authority's spacefaring capabilities.
5: As it turns out, the Authority greatly exaggerated the threat. As a result, the GoI is pissed.