The competition between air and sea transport modes is discussed by H.
Murakami, Y. Matsuse, K. Mukaigawa, and Y. Tsunoda. Their analysis of
air and sea modes is formulated in the form of simultaneous equations. In
the framework of product life cycle, they find that air cargo is at a
developing stage but that sea cargo is at a mature stage. Such
understanding provides practical insights for logistics services providers
with respect to sustainability planning