This study investigates the effects of aviation fluid exposure on aerospace-grade carbon and glass fiber composites. Five critical fluids—hydraulic fluid, dry cleaning solvent, isopropyl alcohol deicer, methyl ethyl ketone (MEK), and a hydraulic fluid/water mixture—were used to simulate real-world environmental conditions. Composite specimens were exposed for durations of 15 days and 30 days. Mechanical properties were assessed through short beam shear tests to determine the interlaminar shear strength (ILSS) of the aged specimen, while fluid uptake was measured gravimetrically. Results indicate that MEK consistently caused the most significant degradation in mechanical properties and the highest fluid absorption for both composite types. Glass fiber composites exhibited greater susceptibility to environmental effects compared to carbon fiber composites. The time-dependent nature of fluid absorption correlated strongly with changes in mechanical properties. These findings highlight the critical importance of specific fluid-composite compatibility testing in aerospace material selection and design. The study underscores the need for enhanced protective strategies and long-term durability assessments to improve the reliability and performance of composite structures in aerospace applications. Future research directions are suggested to address these challenges.