Delta and Northwest Airlines are said to be close to a merger agreement that would create the world’s largest carrier.

The two US carriers have shared details of the proposed merger with the Air Line Pilots Association, Bloomberg reported.

A combination of Delta, the third-largest US carrier by traffic, and Northwest, ranked fifth, would leapfrog American Airlines as the world's biggest airline.

Union representatives are studying how the workforce from the two firms could be meshed together, a deal that is expected to mean substantial job cuts, Bloomberg said.

It is thought that an announcement on the merger could come within weeks.

Both airlines are acutely conscious of generating support from the pilots for any deal.

Of chief concern for pilots is their seniority within the airlines, which helps to determine pay, work schedules and the size of aircraft they fly.

Pilots cannot transfer their seniority if they join another carrier.

Michael Derchin, an analyst for FTN Midwest Research Securities, in New York, said in a report last week that pilots may support similar mergers, if carriers guaranteed "stakes in the combined carriers, some job protection and higher wages".

Doug Steenland, the chief exective of Northwest, told employees last week that industry consolidation was “highly likely''.

Richard Anderson, the chief executive of Delta, also speaking last week, said that Delta “will only go ahead if a merger meets our goals to strengthen the company and create job security for both companies' employees”.

Neither airlines would comment on the proposed merger.

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