During Covid European planes were flying to keep their slots https://www.theguardian.com/environment/2022/jan/26/airlines-flying-near-empty-ghost-flights-to-ret

During Covid European planes were flying to keep their slots https://www.theguardian.com/environment/2022/jan/26/airlines-flying-near-empty-ghost-flights-to-retain-eu-airport-slots https://www.theguardian.com/environment/2022/jan/26/airlines... Another one is to keep communication satalite slotes. If you loose a slot another country can claim your orbit.