Ultrasonic guided wave techniques are universally applied in the framework of structural health monitoring to detect internal defects. In the case of kissing bonds or closed delaminations and incipient surface breaking cracks, the common identification of modifications in the Lamb mode propagation characteristics may not be straightforward, and defects can be missed. In such cases, other concepts of Lamb wave propagation can be proposed. Recently, experiments showed that kissing bonds and clapping contacts give rise to nonlinear features at the defect location, causing high-frequency ultrasonic radiation into the ambient air (Solodov et al. 2007, 2012). This radiation, often referred to as Nonlinear Air-Coupled Emission (NACE), can serve as a nonlinear tag to detect the defects. The present study provides a numerical implementation and simulation of NACE using a 3D time domain model for the nonlinear Lamb wave propagation in cracked or delaminated samples in combination with a spectral solution for the transmission into the ambient air. The model confirms the NACE radiation patterns observed in experiments and allows us to demonstrate how different types of defects, defect dimensions, etc. can be discerned from the NACE radiation patterns in different orientation planes.