  In the sub-TeV regime, the most widely used hadronic interaction models
disagree significant lying their predictions for post-first interaction and
ground-level particle spectra from cosmic ray induced air showers. These
differences generate an important source of systematic uncertainty in their
experimental use. We investigate the nature and impact of model uncertainties
through a simultaneous analysis of ground level particles and first interaction
scenarios. We focus on air shower primaries with energies close to the
transition between high and low energy hadronic interaction models, where the
dissimilarities have been shown to be the largest and well within the range of
accelerator measurements. Interaction models are shown to diverge as several
shower scenarios are compared, reflecting intrinsic differences in the model
theoretical frameworks. Finally, we discuss the importance of interactions in
the energy regime where the switching between models occurs (<1 TeV) and the
effect of the choice of model on the number of hadronic interactions within
cosmic ray induced air showers of higher energies.
