1. Department of Industrial and System Engineering, Hong Kong Polytechnic University, Hong Kong, China.
2. School of Aviation, Massey University, Palmerston North, Auckland, New Zealand; and Aviation Policy Research Centre, The Chinese University of Hong Kong, Hong Kong, China.
3. Department of Economics, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil.
4. School of Accounting, Economics and Finance, University of Wollongong, Wollongong, NSW, Australia.