Based on the analysis of spending, which method was NOT discussed to reduce costs for air transportation?

Changing the main transportation mode to train is not typically classified as a method for reducing costs specifically within air transportation. The focus of the other options revolves around optimizing air transport logistics and leveraging existing air transport frameworks to enhance cost efficiency.

Negotiating contracts with current air transport companies can lead to better rates and preferential terms, ultimately impacting overall costs positively. Consolidating shipments for full plane loads maximizes the utility of aircraft while reducing per-unit transportation costs. Utilizing return flights for increased efficiency enhances capacity management, ensuring that flights are not traveling half-full, which can lead to significant savings.

In contrast, shifting to a different mode of transport, like trains, represents a fundamental change in the logistics strategy and does not pertain directly to methods for improving air transportation cost-effectiveness. This more drastic transition can also overlook the unique benefits and speed of air freight compared to rail, making it less relevant in this context.