Disadvantage is that it utilizes a lot of resources to do its thing. Fuel, rubber, metals, etc. When there's an accident it usually is a good one and can have high numbers of victims (kind of hard to bail out of an airliner). One minor disadvantage is if your airline goes out of business while your away somewhere, it can be difficult to get baack home as the ticket you have is useless and you'll have to pay all over again to come home. The industry is so based on peoples travel habits and desire to travel that it can be up one year and terribly low another. If something goes wrong in the world this industry hurts fast. Demand drops, orders for newer aircraft drop etc.