The International Air Transport Association (IATA) and the European Commission (EC) have stated their desire for the aviation industry to reach net zero carbon emissions by 2050 and in addition these emissions must be reduced by 45% in 2030. In order to reach these goals, all possible contributions to a reduction in carbon emissions are considered. One of these is the Air Traffic Management (ATM) procedure of Continues Descent Operations (CDO). These operations describe a flight path for the approach where there are minimum level flight segments. This paper investigates the maximum possible impact of this procedure for maximum capacity operations. Four different days have been analysed where the individual components of the procedure are investigated; vertical optimisation, lateral optimisation and the combined case. Using ADS-B data from busy days in august of 2019, these procedures are described and simulated using fast-time ATM simulation software Bluesky using Base of Aircraft Data (BADA) performance data and total-energy model. Compared to current operations, vertical optimisation could possibly safe 20% of fuel, lateral optimisation could theoretically safe 16% fuel and the combined case has the potential to safe up to 27% fuel without negatively impacting capacity.