I have created a potion command that makes the player or mob go up into the sky when It is used for 8 minutes. It works for normal potions, splash potions, and lingering potions.

Normal potion command:
/give @p minecraft:potion{CustomPotionEffects:[{Id:25,Duration:9600}],CustomPotionColor:206255255,display:{Name:"\"Potion of Levitation\""}}

Splash potion command:
/give @p minecraft:splash_potion{CustomPotionEffects:[{Id:25,Duration:9600}],CustomPotionColor:206255255,display:{Name:"\"Splash Potion of Levitation\""}}

Lingering potion command:
/give @p minecraft:lingering_potion{CustomPotionEffects:[{Id:25,Duration:9600}],CustomPotionColor:206255255,display:{Name:"\"Lingering Potion of Levitation\""}}

To use a command, paste any of the above commands into a command block, activate the command block, and there you have it!