Table 2.

Airports in the core layer^a.

N0			N1			N2
Airport	Connection	${\mathit{I}}_{\mathit{i}}$	Airport	Connection	${\mathit{I}}_{\mathit{i}}$	Airport	Connection	${\mathit{I}}_{\mathit{i}}$
PEK	142	1	PEK	127	0.69	CAN	150	1
PVG	138	0.69	PVG	127	0.56	CTU	159	0.84
CAN	144	0.73	CAN	130	0.79	SZX	135	0.76
SZX	131	0.64	SZX	122	0.64	PEK	120	0.66
KMG	122	0.57	CTU	147	1	SHA	93	0.38
URC	86	0.42				CKG	132	0.63
CTU	154	0.67				KMG	131	0.54
CKG	128	0.61				XIY	158	0.61
SHA	89	0.43				PVG	153	0.54
XIY	147	0.62
Average	126	0.64	Average	131	0.74	Average	137	0.66

^aThe airport full name and their IATA code is presented in Appendix A.