Whirlwinds are funnels of hot air that serve as a primary way of transport for djinn. With few exceptions, they are invisible to the mundane eye.
To avoid the risk of falling, one must sit back on a whirlwind just like flying carpets. A djinn can adjust the inside of the funnel to their liking and and other humans can travel alongside them in the whirlwind. However, whirlwind travel is sensitive to changes in the Earth's temperature and have been becoming more dangerous due to global warming.
Whirlwinds were first invented by djinn was successors to the more commonly used flying carpets. It was easy to use and unlike a flying carpet, it removed the requirement of the user consciously controlling the flying carpet.
It was first used by Mr. Voddyannoy when bringing John back to his home.
Afterwards, the use of whirlwinds became impractical because of the growing amount of whirlwind failures. To solve this, Faustina sent the twins and Nimrod on a mission to resotre lupuna trees, which would grow to aid whirlwind power.