## 6 Conclusions  
The reduction in GTs is of interest to various stakeholders. Operational constraints and economic, environmental, and social drawbacks that result from extended ground times represent clear risks for the aviation industry. This review points out actual challenges for GTs in passenger air transport and approaches suitable measures to mitigate risks. Namely, risks arise from capacity issues at airports due to increased travel demand. Further, operational irregularities, such as variance in weather or passenger behavior, make it difficult to predict future challenges. This often leads to the occurrence of delays that can easily propagate and negatively affect the entire air traffic system. Costs associated with such system disruptions are significant. Shorter GTs would not only reduce the likely hood of additional costs, but they would also allow for higher profit margins, for example through increased aircraft utilization. Consequently, the challenge is to support \begin{table}
\begin{tabular}{l l l} \hline \hline
**System-Wide Measures** & \\ \hline
**Operations** & & **Data** \\ - Standardized procedures & - & Data analysis and publication \\ - & PSAM & - & Data exchange (ACDM) \\
**Operational measures for individual stakeholders** & & \\ \hline For all stakeholders & & **For particular stakeholders** \\ - & Right planning to stay flexible & - & GSE positioning (GH providers) \\ - & Process flow optimization (PFO) & - & Airport-specific taxi forecast (airport) \\ - & Parallelizing processes & - & Simultaneous consideration of gate reassignment and taxi \\ - & Training of personnel & - & Apron stands instead of gate positions (airline) \\ - & Sufficient personnel for peak times & - & Flight scheduling(airline) \\ - & Measure departure punctuality concerning take-off times & - & Schedule recovery (airline) \\  & instead of push back times & - & Prepare for passengers with reduced mobility (airport, \\  & & GH providers) \\ \multicolumn{2}{l}{**Technical measures for individual stakeholders**} \\ \hline \hline Apron (airstide) & & Terminal (landside) \\ - & Renew terminal building, taxiways, runways & \\ - & Automation of GH (e.g., robot arms) & \\ - & Autarkic turnaround (without GSE) & - & Mobile apps \\ - & Electric taxiing & - & Passenger self-handling \\ - & Underground systems & - & Biometric system \\ - & Cluster aircraft GH interfaces & \\ - & Advanced equipment: Multi-purpose vehicle & \\ \multicolumn{2}{l}{**Boarding**} \\ \hline \hline Operational method & & Aircraft cabin layout \\ - & Boarding strategies (random, outside-in, back-to-front, & - & Seat and aisle configuration \\  & block, reverse pyramid) & - & Door usage \\ - & Consider luggage, groups, seat assignment & - & Connected aircraft cabin (sensors) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Overview of considered measures to reduce ground times in passenger air transport. and implement efficient and timely ground operations and thereby mitigate risks, taking into account that different areas are contributing to the reduction in GTs. First, the whole system is challenged by the necessity of efficient collaboration. Stakeholders must exchange relevant data to be able to better predict future stages and plan accordingly. Suitable measures are the implementation of ACDM, ADS-B, A-SMGCS, or PBM. Moreover, data analytics is a relevant topic. Further, process monitoring and optimization as well as improved planning and scheduling of turnaround and taxi operations and resources (GSE, personnel) are important fields to consider for minimized GTs. The introduction of new technologies is promising as well. The ongoing digitalization offers many opportunities for increased efficiency, including electric taxiing, autonomous operations, robotics, and advanced passenger handling at airport terminals. Increased boarding rates lead to boarding activities forming a critical part of the turnaround process.