General comments

This manuscript presents an observational analysis of pollution transport and vertical structure over the Po Valley using airborne measurements from the EMeRGe campaign, combined with ground-based observations, trajectory calculations, and dispersion modelling. The dataset is valuable, and the manuscript is clearly relevant for the special issue. The multi-platform observational approach provides important insight into vertical layering, recirculation, and plume variability in this complex region.

The manuscript is generally well structured and the results represent a useful contribution to the interpretation of EMeRGe observations and to the broader understanding of pollution transport over the Po Plain. However, the manuscript is some times highly descriptive and would benefit from some streamlining, with a clearer synthesis of its main scientific advances. I therefore recommend publication after minor revision.

Specific comments

1. Line 108: The manuscript states that one of its objectives is the identification of trans-regional and trans-boundary transport to and from the Po Plain. The presented observations and trajectory analyses clearly document regional recirculation and export towards the Adriatic and Alpine regions. However, direct evidence for cross-national impacts remains limited. It would be helpful if the authors could define more explicitly what is meant by trans-boundary transport in this study and distinguish clearly between regional recirculation and transport with potential cross-border implications.
2. Line 194: This multi-tool approach is appropriate and commonly used in aircraft campaign analyses. However, the consistency between these tools is discussed mainly qualitatively. In addition, the models are driven by different meteorological datasets and resolutions. A short discussion of uncertainties would strengthen the manuscript, particularly under the weak-wind conditions typical of the Po Plain.
3. Section 3 contains a detailed and comprehensive description of observed plumes and vertical structures. While this level of detail is valuable, the main conceptual conclusions sometimes remain implicit. In several places the text describes individual plume segments without clearly summarising the broader implications.
4. Line 306-314, 339-349, 408-414: The manuscript uses a combination of trace-gas ratios, aerosol composition indicators, trajectory analysis, and HYSPLIT age estimates to distinguish fresh and aged pollution plumes. It would be helpful to provide a short summary explaining how these indicators were used to identify fresh versus aged air masses for each shuttle.
5. Section 3.1: The multi-platform observational approach is a major strength of the study. The manuscript would benefit from a slightly stronger integration of the different datasets in the interpretation, with clearer statements on how airborne, ground-based, and lidar observations jointly support the conclusions.
6. Section 3.3: This section provides important interpretation. Consider adding one or two sentences quantifying or summarising inferred mixing or recirculation timescales where possible. It may be a proper place to clarify how these conclusions relate to previous Po Valley studies.
7. Section 3.4 discusses the presence of an elevated dust layer and its possible influence on atmospheric stability. This section is useful for providing context for the observed layering, but the connection to the main transport and mixing interpretation could be stated more explicitly. A brief clarification of how the dust layer may have influenced boundary-layer mixing, vertical exchange, or plume persistence during the analysed flights would help integrate this section more closely with the main conclusions of the paper.