Based on the empirical data of 28 international airlines, this paper studies the impact of airline cooperation on Greenhouse gases (GHG) abatement costs under CNG2020 strategy. We propose a Data Envelopment Analysis (DEA) Cross PAC model to discuss the differences in pollution abatement costs (PAC) between arbitrary scene and cooperation scene. The main findings are as follows: 1. Airline cooperation helps to reduce the GHG abatement costs of most airlines. 2. Star Alliance and SkyTeam Alliance can help airlines reduce GHG abatement costs, but the Oneworld cooperation is not effective. 3. The GHG abatement costs of Iberia, British Airways, TAP Portugal, Finnair, Emirates and Singapore Airlines are zero. (C) 2018 Elsevier Ltd. All rights reserved.