To reduce aircraft emissions to the atmosphere, the fuel burn from aircraft has to be reduced. For long flights, the cruise is the phase where the most significant reduction can be obtained. A new horizontal profile optimisation methodology to achieve lower emissions is described in this article. The impact of wind during a flight can reduce the flight time, either by taking advantage of tailwinds or by avoiding headwinds. A set of alternative trajectories are evaluated to determine the quickest flight time, and therefore, the lowest fuel burn. To determine the expected amount of fuel reduction, the performance databases used on actual FMS devices, were used. These databases represent the flight performance of commercial aircraft.