Large landslides are known to generate powerful air blasts capable of causing damage far beyond the landslide runout. In many cases, observations of tree destruction are the only evi-dence to quantify the air blast danger. In this study, we proposed an approach to assess the air blast power using the tree breakage information, including the eigenfrequency prediction, tree motion calculation and breakage conditions. The tree is modelled as a flexible beam with elastic support at the tree base. Large tree deflection is accounted for when calculating the air blast loading and two failure modes (bending and overturning) are defined. Modelling results illustrated that tree eigenfrequency is always close to the air blast frequency, leading to a dynamic magnification for tree deformation. This magnification effect is greatly influen-tial in a weak air blast case, but the large tree inclination resulting from strong air blast load-ing would weaken the effect. Additionally, both failure modes are likely to occur and the exact failure mode of trees depends heavily on their bending and anchorage resistance. Therefore, further measurements need to be conducted on the biometric and mechanical characteristics of trees, which will improve the accuracy of air blast hazard assessment.