Fan stopped working. Turned out my lazy-self got a piece of a shreddie stuck inside. Regular for me; irregular for a laptop.
Everything went according to plan except the driver (P5) stripped. iFixIt dispatched a replacement NEXT DAY! Wow, what service.
If you have multiple P5-bolt-burdened devices though, get the high-end driver.
Also there's a rubber air guide/seal on the original Fan that you have to peel off and stick to the new fan - as the replacement fan doesn't include it - no biggie, just FYI!
MacBook Air 11" (Mid 2011-Early 2015) Fan
T5 Torx Screwdriver
P5 Pentalobe Screwdriver Retina MacBook Pro and Air