What causes the deterioration and moisture infiltration in fixed-wing and rotary-wing aircraft?

The correct choice is seals, as they play a crucial role in preventing moisture infiltration in both fixed-wing and rotary-wing aircraft. Seals are designed to block moisture and contaminants from entering critical areas of the aircraft structure, particularly in joints and gaps around windows, doors, and other access points. Over time, these seals can degrade due to environmental exposure, mechanical wear, and aging, leading to improper sealing and allowing moisture to infiltrate areas where it can cause corrosion and other forms of deterioration.

This moisture infiltration can lead to serious issues, including corrosion of metal components, deterioration of insulation materials, and reduced structural integrity. Regular inspection and maintenance of seals are essential practices in aviation to ensure that they remain effective, thus protecting the aircraft from potential damage caused by moisture exposure.