This page of the guide to Far Cry 6 explains how to unlock the Wingsuit and Parachute. Both these gadgets are very helpful in flying and jumping from high altitudes safely.
You will unlock the parachute first during the introduction to the campaign. You will receive it in the DU or Die quest. The parachute does not activate automatically - you must press Circle/B in mid-air. This is a great gadget if you want to jump from a tower, viewpoint or roof of a large building without the risk of dying if you crash on the ground. You can also glide and steer the parachute to determine the precise landing spot.
The Wingsuit is more interesting than the parachute, but unfortunately you won't get it along with the progress in the campaign.
You have to go to one of the big rebel camps later in the campaign, i.e. the ones where the camera switches to TPP view. One of the unique locations in each camp is the Construction Desk, where you can order blueprints for buildings. Select Hideout Network from the list of projects. Purchasing this project will unlock the Wingsuit.
From this point on, you can activate the Wingsuit by pressing the left analog stick (L3) while flying. It allows you to stay in the air much longer and glide across greater distances than the parachute. Remember to switch to the parachute before hitting the ground, though.
Once you have the Wingsuit, the game will also give you the Air Drop option, which will appear when you browse the map and choose fast travel points. This way, you can move up in the air right away without having to look for high jump points or using a plane or helicopter.