Like you'd expect, there are all sorts of different variants of airforce backpacks and rucksacks. Depending on what the specific situation requires, airforce operators may need a larger pack for longer missions, or smaller more compact options that carry a smaller load, but are easier to maneuver with. Typically a lot of airforce backpacks also come in a streamlined style as well as different colorways to their army and navy counterparts.
Depending on what's being carried in a backpack, they can weigh anywhere between 20 to 100 pounds. Being designed for flight operators, a lot of airforce packs come with enough space to pack a parachute and all of the necessary equipment for an air to ground transition. But if you're not looking to do any skydiving or flight to floor traversing, they can be perfect because of their typically lightweight and robust materials.
Choosing the best airforce backpack for you means looking at what you're specifically going to be using it for. Will you be jumping out of planes, will you be taking it on long hikes, or will you be using it on a daily basis to carry your school books? The right backpack for you is going to be the one that provides the perfect cross road between practicality and enjoyment. First of all, look at the carrying capacity of all the bags and decide how much you need. From there you can look into whether or not you'd like or need all of the extras that airforce personnel require, or if you want something a little more basic. Finally, you should then consider how it looks (particularly if you're buying it for aesthetic purposes). Once you've asked yourself all of these questions, you should be able to arrive at a backpack or a smaller choice of backpacks that are perfect for you.
In a professional capacity, airforce backpacks are usually utilised by pilots and airborne operators. They need to be compact and subtle, but also with a big enough carry space to see that everything necessary is on-board. In a lot of cases, those in the airforce may find themselves grounded in a war zone, and having a small backpack with minimal supplies isn't the greatest position to be in. But jumping out of a plane also means you don't want to be burdened by a huge pack on your back. That's why these backpacks are typically smaller than army packs, but can have quite a bit more carrying capacity than you might expect from first glance.