I just obtained the Eye of Flugel and once my Flugel tiara runs out of flight, it doesn't let me fly even with a 3/4 full Greater Band of Mana and the Eye of Flugel in my inventory. The book says I should be able to fly with an empty flight bar at a higher mana cost. I'm currently running the latest release of All the mods 9 with Botania version 1.20.1-441-FORGE.