Over the duration of the last year research regarding the en route delay absorption capabilities of the MUAC airspace for Schiphol inbound flights has been performed. Delay absorption currently takes place in the lower airspace, where as a result air traffic controllers and pilots experience increased workloads during one of the most critical periods of a flight. This in combination with the expected fuel inefficiency of delay absorption in the lower airspace resulted in this research to investigate the options of moving delay absorption away from the lower airspace, into the en route airspace. The MUAC airspace is all airspace above FL245 over The Netherlands, Belgium, Luxembourg and West-Germany, encompassing Schiphol inbound flights entering the LVNL airspace (all airspace over The Netherlands up to FL245) from the South, East and North. Traffic data from two sample days was selected (one in high season and one in low season) to reflect the different traffic patterns occuring throughout the year, based on which the planning conflicts were determined. From these planning conflicts the amount of required delay absorption has been obtained, and used as an input to determine which way of en route delay absorption should be used. A range of delay absorption measures has been defined and evaluated: linear holding and dropping for all routes, and detouring and turtling for selected Northern routes. Linear holding means only slowing an aircraft down to the Maximum Range Cruise speed at most, and dropping represents both slowing an aircraft down while lowering its altitude by 2000 ft across its trajectory within the MUAC airspace. Detouring and turtling are the equivalent of linear holding and dropping, respectively, however executed on an extended trajectory. Changing the trajectory of an aircraft may result in conflicts with other traffic, hence it was decided only to use these measures for the Northern routes. This part of the MUAC airspace has a lower traffic density in general, and was the only airspace that could reasonably be provided with detours. The changes were implemented in the scenarios, which were run in the BlueSky Open Source ATM Simulator to gather data on fuel consumption (using Eurocontrol’s Base of Aircraft Data), air traffic controller communications workload, and the number of conflicts with other traffic. The data obtained from the delayed scenarios has been compared to the original scenario to see how the variables were affected by the delay absorption. The delay absorption within the MUAC airspace was found to be 0.4 s/NM for linear holding and 0.7 s/NM for dropping. For the three routes through the Jever sector that were found eligible for detouring and turtling, an additional 8 seconds should be counted for each additionally flown nautical mile. Fuel consumption has been compared to the fuel consumption in the original scenario, from which a slightly reduced fuel consumption was found for linear holding (-0.1%), but a significantly lower fuel consumption for dropping and turtling (-45% and -50%, respectively). This strong reduction in fuel consumption is caused by the earlier initiated descent, during which the aircraft can throttle back to idle thrust. Detouring was found unfavourable in terms of fuel (due to the additional path length), but is nevertheless an effective means of delay absorption. The communication workload was generally found to strongly increase during MUAC peak loadings. Adding more work when a controller is already at his/her busiest is not very desirable, which is why it is unlikely that delay absorption during peak loading can be implemented in the way it was simulated. However, off-peak workloads were sometimes found to be even lower than in the original scenario. This can be explained by the reduction of the number of conflicts, due to which some of the workload assigned for resolving conflicts could be eliminated. During these times of day en route delay absorption would be more than just feasible; it would be very desirable. The ability to predict the change in communication workload has been assessed by computing the correlation between expected and actual change in communication workload, as well as between traffic density and actual change in communication workload, but no relation was found to be strong enough to give a representative indication of the actual change in workload. Overall, the total number of conflicts during linear holding and dropping runs for the low season day were found to lower by 1.1% and 0.4% respectively. The high season saw an overall increase of 0.7% of the total number of conflicts. It is thus expected to be favourable for other traffic if en route delay absorption is performed during low season days, but mostly unfavourable during high season. The Jever sector was the only sector to be equipped with detouring and turtling options, and during all scenarios except for the August linear holding and dropping scenarios a reduction of the total number of conflicts was observed. It can be concluded that when care is taken in when and how en route delay absorption is implemented, it most definitely shows potential to (partially) replace delay methods in the lower airspace.