Table 1.

COVID-19 pandemic periods in China.

Network code	Period name	Time period	Airport numbers	Total Flight frequency (ten thousand)
N0	Normal period	Jan 01, 2019–Dec 31, 2019	237	533
N1	Pandemic period	Jan 01, 2020–Feb 28, 2020	228	58
N2	Recovery period	Mar 01, 2020–31 Dec 2020	238	298