DALLAS — Southwest Airlines raised its third-quarter revenue forecast on Thursday, announced its board authorized $2.5 billion in share buybacks and detailed a host of changes to its business model as it seeks to fend off activist Elliott Investment Management.

The airline said it expects unit revenue to rise as much as 3% in the third quarter over the same period last year, up from a previous forecast of a decline of as much as 2%.

The carrier also said it would add Bob Fornaro, a well-respected industry veteran who previously led Spirit Airlines, to its board of directors. Southwest and Fornaro go back more than a decade. He had served as CEO of AirTran, the airline Southwest combined with in 2011, and was a consultant to Southwest after the merger.

Southwest executives are presenting their vision for the company’s future at the airline’s Dallas headquarters on Thursday in an investor day presentation. CEO Bob Jordan and Southwest’s other senior leaders are under increasing pressure from Elliott, which has called for a leadership change at the carrier.

Southwest executives will try to convince investors that it is on the right track to boost profits and increase revenue. Over the summer, it unveiled dramatic changes to its more than half-century-old business model, including assigned and extra-legroom seats, which could generate more revenue for the carrier.

In its presentation on Thursday, Southwest stood firm on its long-standing policy of allowing customers to check two pieces of luggage for free, saying it “generates market share gains in excess of potential lost revenue from bag fees.”

A day earlier, Southwest told staff it will slash its service in Atlanta next year and could cut more than 300 flight attendants and pilots from the city in an effort to reduce costs.

Earlier this month, Southwest’s executive chairman and former CEO Gary Kelly said he would step down by the end of next year. Elliott later told Southwest mechanics’ union that it still wanted a leadership change at the top of the carrier. The firm didn’t immediately comment on Southwest’s strategy presentation it released Thursday.

— CNBC’s Rohan Goswami contributed to this report.