When Lord Hanuman Indulged in a very struggle with Ahiravana, he learned that it was impossible to kill Ahiravana in the struggle, and there have to be some magic formula about his death. When Vayu noticed this, he caught Hanuman in the air and brought him down safely and securely. https://www.youtube.com/watch?v=ufkmD95y7fE&t=1s