Air Crawling is a glitch that allows you to get height infinitely
To air crawl you need to Jump > Double jump > Pull slingshot > Hold L3 > Cancel 1st person
The faster you do it the faster you get height as it preserves the speed of your jump when you do it

If you use the sky flyer during an air crawl you will snap down to the height of the first jump
this allows you to clip troug floors at certain locations (example for the final boss door)

below are videos by: Squid and Surreal