This investigation concentrates on the attachment-line flow behaviour under wind tun- nel and flight conditions. A turbulence model for incompressible, equilibrium flow'was developed for low Reynolds number down to and including relaminarisation. This was then extended to compressible flow using CFD to analyse experiments in which the heat transfer was measured. The extension is based upon the introduction of two Reynolds numbers to correlate turbulence in the inner and outer regions of the viscous layer. This requires the addition of just one constant, which is determined from the experimental heat transfer data. The turbulence model was then used to calibrate an approximate heating prediction method based upon the reference temperature concept. This method was then used to determine the minimum conditions for sustainable turbulent attachment-line flow in presence of large sources of disturbance, such as trip wires. It has been shown that existing criteria for the minimum conditions provide excessively optimistic predictions. Therefore new, more accurate criteria were proposed.