(Reuters) - Southwest Airlines' shares rose about 7% in premarket trade on Monday after the Wall Street Journal reported that activist investor Elliott Investment Management had built a nearly $2 billion stake in the U.S. carrier.

According to the Journal's report on Sunday, Elliott is one of Southwest's largest investors and plans to push for changes aimed at reversing the airline's underperformance.

Southwest and Elliott did not immediately respond to Reuters' request for comment.

Southwest, one of the largest U.S. airlines, has been grappling with higher costs and slower-than-expected revenue growth due to delays in 737 MAX aircraft deliveries from planemaker Boeing.

The carrier has said delivery delays have led to "significant challenges," leaving it overstaffed and forcing it to temper its growth plans.

The Dallas-Texas-based company's shares have fallen nearly 4% this year, compared with an about 12% rise in the S&P 500 index.

"We are not surprised by the activist interest in Southwest given the very strong franchise with valuable tangible and intangible assets," Raymond James analyst Savanthi Syth wrote in a note.

The Journal report noted that Elliott, one of the world's most prominent investors, plans to engage with Southwest's management team.

The activist investor is known for pushing for changes in companies to boost shareholder returns.

Southwest, however, is not alone in struggling with Boeing delays. Rival United Airlines also took a $200 million hit in the first quarter from the disruptions at Boeing.

Despite these challenges, the airline sector expects to do well over strong demand for summer travel.

Southwest shares trade about 19.52 times their forward profit estimates, compared with United's 4.74 and above the industry multiple of 7.19.

(Reporting by Nathan Gomes in Bengaluru; Editing by Tasim Zahid)