This paper studies the evolution of fleet-level emissions from aviation under different scenarios of aircraft technology availability and fuel price variation. The aim is to assess the efficacy of introducing advanced technology aircraft as a means to reduce total emissions while still serving increasing passenger travel demand. Particularly, this paper explores the potential existence of an effect in the aviation industry similar to the so-called the Jevons' Paradox, in which the profit-seeking airline modeled here uses a larger number of more fuelefficient aircraft so that the increasing number of flights overwhelms the fuel efficiency gains of the individual aircraft. Simulation results confirm that, while advanced technology aircraft would improve the emissions efficiency of the airline fleet, the advance technology alone would not be sufficient to reduce total fleet-wide CO2 emissions. This finding implies the need for other initiatives (e.g., operations changes, alternate fuels, and carbon policies) to provide incentives to airlines to reduce CO2 emissions.