*1.1. Current Situation*

ATCOs are responsible for maintaining separations between aircraft. Today, spacing to severe weather is the responsibility of the pilot in the event of occurring convective cells. When adverse weather occurs on the aircraft's planned or assigned route, the pilot decides whether to fly through it, fly over it, or avoid it to the left or right. In addition to the onboard weather radar, pilots can also use external live weather applications such as eWAS, which can transmit current weather data to the cockpit via a fast SatCom data link [12].

The ATCO clears this avoidance maneuver and ensures that it does not result in critical separation infringements with other traffic. Center controllers, responsible for approach and lower and upper airspace, have no weather radar available for their sectors. The systems, visualizations, and procedures developed by the German Aerospace Center's (DLR's) Institute of Flight Guidance presented in this paper use available weather information to initiate four-dimensional route rescheduling and arrival sequencing. These tools provide appropriate rerouting advisories for ATCOs at an early stage using forecasts from 30 to 60 min in advance so that pilots do not have to avoid adverse weather situations at short notice. This relieves both the pilot and the ATCO and allows them to react in sufficient

time in advance and at a reasonable distance so that rerouting trajectories stay safe and efficient [13].
