Methods and systems (10) based on guided wave thermography for non-destructively inspecting structural flaws that may be present in a structure (15). For example, such systems and methods may provide the ability to selectively deliver sonic or ultrasonic energy to provide focusing and/or beam steering throughout the structure from a fixed transducer location (12, 14, 16). Moreover, such systems and methods may provide the ability to selectively apply sonic or ultrasonic energy having excitation characteristics (FIGS. 11 and 12) which may be uniquely tailored to enhance the thermal response (FIGS. 5 and 7) of a particular flaw geometry and/or flaw location.