Macbook Air Fan running frequently and loudly
The easiest explanation is that the MacBook Air is by no means a performance Mac. Their processors range from 1.1 GHz to around 1.8GHz. Some have 8 GB of RAM, while others have just 4 GB, and some (like one of my family member's MacBook Air) have only 2 GB. Graphics processing units and other parts follow suit. In short, the MacBook Air sacrifices performance for portability, which isn't necessarily a bad thing, but it does mean that if you try to do a lot on it or preform hardware-intensive tasks on it, it will get pretty warm and the fans will go pretty high.