what is the difference between fixed wing mode and standard mode? Is there any advantage in using fixed wing mode?

It simulates a fixed wing aircraft - suggest you read up on it before using it. Vey cool effect but be sure to know how to use it in a very wide open area.

Hi Pezza, thanks for bringing this query to us.  The fixed wing mode was introduced first to Mavic Pro then to Mavic Air. As of the time being this is not present with the latest Mavic recently launched. It is kind of like flying your drone like a plane. Instead of left and right just moving to the left/right, it "banks" like a plane does when it turns. So, at an angle (to the horizontal). The same for up and down. They are more like climbing and diving in a plane, than just moving straight up or down as you do with a quadcopter​ like the Mavic. You may also click this Forum discussion of our co-pilots for more inputs. Thank you for continued support. Fly safe always.

Fixed wing mode is like sitting in the cockpit of a full size aircraft. When you bank and turn, the horizon moves accordingly.

Just like my early experiments with FPV in r/c model aircraft so many years ago, it is great fun

Fixed wing is a bit of fun if your are using FPV goggles