This article deals with the monitoring of the composite wing skin-to-spar joint in unmanned aerial vehicles using ultrasonic guided waves. The study investigates simulated wing skin-to-spar joints with two different types of bond defects, namely poorly cured adhesive and disbonded interfaces. The bond-sensitive feature considered is the ultrasonic strength of transmission through the joints. The dispersive wave propagation problem is studied numerically by a semi-analytical finite element method that accounts for viscoelastic damping, and experimentally by ultrasonic testing that uses highly durable, flexible macro fiber composite transducers. The discrete wavelet transform is also employed to de-noise and compress the ultrasonic measurements. Both numerical and experimental tests confirm that the ultrasonic strength of transmission increases across the defected bonds.