Aircraft get delivered with full kits. For our A320's, the kits come in silver metal suitcases, our E190's come in larger blue bags because of the foam plugs for the engine exhausts. The kits will typically consist of covers for the various probes, ice detectors, engine intake and exhaust, and APU exhaust. I also believe our A320 kits come with the fuel tester tool but we have to remove them as we are not a DG
carrier so in order for us to COMAT them, we can't have the fuel test tools in there with the potential of having left-over fuel. There are other covers as well, but they may not apply to all aircraft. These kits were removed off our aircraft as standard equipment for weight savings (I know, I know, really stupid move, but I didn't make that decision...I did fight it though!).
Now, we DO
cover things up during an RON if weather is going to be an issue. For example, if we have an aircraft that is going to be touching down in a city where there is supposed to be snow or ice overnight, maybe a dust storm, they get covered up. But what you have to remember is that planes are on the move A LOT. In a 24 hour day, it is actually common for a plane to be on the move over 12 hours. When that plane settles down for the evening, a lot of times MX
crews are working on the plane. Now, if a plane is in a hangar, it is REQUIRED (by our airline) for engine covers to go on unless work is being performed on the engine or there is an engine change. Why? Because if the foam system goes off, it prevents the foam from going in the engine which would require an engine change. 2 engines per plane, 3 planes in the hangar, 6 engines would need to be changed which would have impacts on the operational schedule.
aircraft have the potential for being on the ground for days even weeks at a time before being flown again, and are also on ramps where there isn't that much activity compared to a terminal ramp where you have baggage carts, belt loaders, maintenance trucks, or even hangars where you also have a lot of hustle around (animals don't like hustle). Smaller planes have a higher risk of having birds nesting in various holes, insects getting in a building nests, and stuff being exposed to weather for a longer period of time.
Hope that helps!