The aerodynamic performance of an aircraft wing is influenced by the angle of attack (AoA), which directly affects lift, drag, and overall efficiency. This study presents a theoretical analysis of the effect of AoA on a symmetric thin aerofoil using aerodynamic models including Thin Aerofoil Theory and Lifting-Line Theory are discussed. Results are discussed under three regimes; linear AoA range where lift increases proportionally while maintaining steady improvement in lift to drag ratio, pre-stall regime where partial flow separation takes place by reducing lift growth, near-stall where flow separation causes deterioration in aerodynamic efficiency. The study highlights the importance of wing geometry including aspect ratio, camber, and sweep angle. Understanding complex interactions between AoA, lift generation, drag forces, and wing geometry is crucial for optimizing aircraft design and improving aerodynamic performance.