(Reuters) - Southwest Airlines' ( LUV ) 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 ( LUV ) largest investors and plans to push for changes aimed at reversing the airline's underperformance.

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

Southwest ( LUV ), 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 ( BA ).

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 ( LUV ) 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 ( LUV ) management team.

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

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

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

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