An experimental study has been conducted into the structure of jet flames in a cross air-flow. The cross-flow and fuel-jet velocity were varied, to determine their effects on the trajectory and inner structure of the flame. Direct colour and reactive Mie scattering techniques were employed for visualising the flow. Apparently the trajectory is significantly influenced by the magnitudes of initial momentum and flame buoyancy. The organised vortices inside the jet flame in a cross-flow of air were observed at low jet velocity. The location of generation of the inner structure changes from the lee side to the windward side as jet velocity increases. Two vortex systems are responsible for the flow behaviour in this flow field.