Open Sky was a 24th century Akritirian terrorist group with the objective to free the people of Akritiri from an undemocratic government.
In 2373 members of this group acquired paralithium from an Akritirian freighter that they used to synthesized a Trilithium explosive.
This device was used by two of its member in the bombing of Laktivia recreational facility, killing forty-seven off duty patrollers.
The group was actively hunted by the ruling government of the planet.
Two known members of Open Sky were family members Piri and Vel. (VOY episode: "The Chute")