A couple of days ago I was wondering that if a merger occurs between DELTA and NORTHWEST, they will create the world´s biggest airline, and the destination network will be so extensive, they will become US flagship carrier as PAN AM and TWA were on their time.
Imagine Delta´s European network + Northwest Asian network.
This will be a sample of the destinations.
EUROPE : MAD,BCN,CDG,LYS,NCE,FRA,MUC,ZRH,STT,MXP,FCO,VCELGW,AMS,BRU,SVO,ARL,IST,ATH,MAN,SNN, DUB

ASIA
NRT,KIX,NGO,PEK,PVG,HKG,KUL,SIN,SEL,TPE,BKK,KAO,

LATIN AMERICA
MEX,EZE,GRU,GIG,BOG,SCL,CCS,etc.

AFRICA DL important codeshare agreement with SAA & NW destinations operated by KLM.

However I think this merger couldn´t pass, because the government will never approve it and besides there will be a European conflict of interest, because of DL European partner AF, and NW big alliance with KLM.