The present study concerns the application of Large Eddy Simulation (LES) and Implicit LES (ILES) to engineering flow problems. Such applications are often very complicated, involving both complex geometries and complex physics, such as turbulence, chemical reactions, phase changes and compressibility. The aim of the study is to illustrate what problems occur when attempting to perform such engineering flow calculations using LES and ILES, and put these in relation to the issues originally motivating the calculations. The issues of subgrid modeling are discussed with particular emphasis on the complex physics that needs to be incorporated into the LES models. Results from representative calculations, involving incompressible flows around complex geometries, aerodynamic noise, compressible flows, combustion and cavitation, are presented, discussed and compared with experimental data whenever possible. In addition, we also compare predictions from LES and ILES with conventional Reynolds Averaged Navier-Stokes (RANS) models and Detatched Eddy Simulations (DES) for academically challenging flows, such as the flow around a cylinder and around a surface mounted 3D hill. It is found that both LES and ILES predict these flows more accurately than RANS and DES, and include more information about the dynamics of the flow.