Exemplary embodiments of a system and method are provided for detecting cracks and crack propagation in aircraft structures subject to repetitive stress. A method for detecting onset or propagation of defects in a structure includes monitoring the structure with an infrared sensor to provide thermal data of the structure within a field of view of the infrared sensor. A processor is used to process the thermal data memory to extract features from the thermal data and utilize at least one machine learning model to detect onset or propagation of defects in the structure. A system includes an infrared sensor having a field of view of the structure and a processor coupled to the infrared sensor and a memory, which contains instructions that cause the processor to process thermal data from the infrared sensor to extract features from the thermal data and utilize at least one machine learning model to detect onset or propagation of the defects in the structure.