Single-Aisle Cruise flight levels and speeds
Are optimum cruise altitudes routinely available for short haul ops in crowded airspace (i.e. Europe) where the stage length is sufficient? Or are cruise altitudes frequently limited to non-optimum flight levels due to other traffic?
Similarly, are A320s or 737NGs cruise speeds impacted by slower aircraft such RJs, older 737s and single aisle MD aircraft?
Does anyone know if this data exists in the public arena?