Aluminium alloy is widely utilized in aerospace engineering because of its lightweight and high specific strength. Creep and fracture of aluminium alloy serving at high-temperature conditions are always a long-term concern. Especially creep crack nucleation and growth behaviours under high out-of-plane constraint levels are the significant processes to generate failure. High-resolution nanometre computed tomography equipment can be adopted for obtaining the three-dimensional morphology and information on damage to investigate the mechanism of creep crack growth. According to the obtained results, the stress-field strength has an impact on creep crack propagation under high out-of-plane constraint levels.