In 2013 JFK Traffic Statistics.
AA Domestic 4,345,100
AA International: 3,208,371
AA totals out of JFK: 7,553,471
DL Domestic: 7,244,249
DL International: 4,396,939
DL totals out of JFK: 11,641,188
Now lets see what US did out of JFK:
US Domestic: 877,083.
So PMAA and PMUS carried 8,430,544 out of JFK.
EWR Statistics:
AA Domestic: 1,038,891
US Domestic: 1,349,425
Total Combined: 2,388,316
DL Domestic: 1,338,847
DL International: 188,780
DL Total: 1,527,627
Sidenote UA carried over 24,500,000 out of EWR.
LGA Statistics:
AA Domestic: 4,692,070
AA International: 293,350
AA Total: 4,985,420
US Domestic: 2,733,865
PMAA and PMUS carried a total of 7,719,285 passengers.
DL Domestic: 10,344,741
DL International: 260,258
DL Total: 10,604,999
So lets add it all up:
AA/US carried a total of 18,538,145
DL carried: 23,773,814
So just UA alone at EWR carries more passengers than DL at all THREE NYC Area Aiports.
So the out of the NYC Region they carried the following: (this includes SWF also)
AA: 13,577,782
US: 5,044,907
DL: 23,852,436
http://www.panynj.gov/airports/pdf-traffic/ATR2013.pdf