It is possible for an airplane to get infested by animals?
Yes, I have personally worked on multiple aircraft that were infested by animals.

All of these aircraft were small planes, single engine Cessnas for example. A typical example would be one or two small mouse nests in the wings. I also found at least one wasp nest in an aircraft wing.

The worst I ever saw was a Mooney that had extensive mouse nests throughout the airframe. That aircraft had been unairworthy for at least a year by the time I saw it.

That Mooney ended up being parted out and scrapped, largely because of extensive corrosion in the wings which was either caused by, or aggravated by, the mouse nests. Urea can induce corrosion in aluminum, and finding a mouse nest or other evidence of rodent activity should prompt closer inspection. All the other instances of mouse nests that I have found in airframes were in aircraft that flew several hundred hours a year and these did not suffer any major damage.

I have also heard stories from many pilots and mechanics of finding birds nests—for example in engine intakes or the empennage—and of rodents chewing into or through electrical wiring. There is also the classic warning to check the pitot tube in case a mud wasp has clogged the intake with a nest. I have never witnessed any of these occurrences myself.

The mud dauber wasp is notorious and is suspected of being a contributing factor in at least one fatal airline accident that I am familiar with: Birgenair Flight 301.


Photo source, courtesy of the FAA

Many means of prevention are available, including typical pest prevention methods such as traps and poisons—in my experience all reserved for use in the storage hanger. The most aviation specific forms are the various covers used to protect pitot tubes, engine inlets, etc.


Photo source, courtesy of the FAA

As far as the possibility of animals surviving, I suppose the odds are low. I have never encountered a live animal in an airplane (pets excepted). For any animal stowing away on a pressurized aircraft operating at high altitude I should think the low oxygen partial pressure and temperature would both discourage survival outside the pressure vessel.

Some flights, particularly international ones, apparently make a practice of spraying some form of pesticide in the cabin to kill mosquitoes and other unwanted creatures.