Separatists fighting against a superpower country would probably do the following,
1. Devise a plan to take hostage a sizable group of citizens of the superpower country that they were fighting against for the purposes which include exchanging the hostages with their comrades currently imprisoned by their superpower enemy.
2. They got a base in a neighboring country which borders their occupied homeland. Preferably, the host country of their base is unfriendly towards the superpower they were trying to chase out of their homeland. The host country, preferably should be controlled by people of the same ethnic group as them, thus sympathetic to their cause.
3. Recruit sympathizers such as co-religionists from other countries who among them include a person who is capable and in a position to pilot an airliner mostly full of citizens of the superpower to their base just across the border to their homeland.
4. This sympathizer would then carried out the
Ten steps which include flying along borders
5. Once the plane had landed somewhere near their base, they would transport the hostages to several separate locations to make it hard for the superpower to launch a military rescue mission against them.
6. A demand would then be made to the superpower, probably just hours after the hostages had been securely placed at several locations across the separatists' host country. The demand must be made in secret to avoid the superpower from acting rashly such as launching a military rescue mission across the border of the host country which itself is close and protected by a still militarily formidable former superpower ally.
7. A deal must be struck with the superpower for the negotiations between them be carried out in secret to avoid any pesky third party from interfering while the negotiation process was still ongoing. The superpower must be persuaded to act as if its officials do not know anything about the whereabout of the plane and all those onboard.
8. Once a deal had been struck and the superpower had fulfilled its end of the bargain, the hostages would be released at the border between the separatists' occupied homeland and that of their host country.
Note: As for the person who flown the aircraft to the secret location, he probably had arranged for his family members to move to another country where he will join them later, after the issue had been settled.