High-cost fuel, consumers'complaints or dissatisfaction, the economy's downturn and other factors cause the two companies to seek merger.
DELTA Airlines and Northwest Airlines have approved a merger deal to create the world's largest airline by traffic.
The combined airline will be led by Delta.
The alliance will create “America's premier global airline”, Delta said, if the $US17.7 billion deal passed regulatory approval.
The deal comes at the same time as skyrocketing fuel costs, a suffering economy and increasing dissatisfaction among travellers, which have together put a chokehold on the airline industry.
