Southwest Airlines earned a net profit of $608 million in the second quarter, up 30.8% over net income of $465 million in the 2014 June quarter, as the company surged to a 28.2% pre-tax return on invested capital (ROIC) for the 12 months ended June 30.

The ROIC was 11.1 points higher than the 17.1% ROIC Southwest reported for the 12 months ended June 30, 2014. “Overall, our network performance is exceptional,” Southwest chairman, president and CEO Gary Kelly said in a statement. He outlined growth plans for 2015 and 2016: “For this year, we are growing our ASMs approximately 7% year-over-year … As we continue to optimize our network, we are currently planning to grow our total 2016 ASMs in the 5%-6% range year-over-year with the goal to sustain strong margins and ROIC levels in line with 2015.”

Southwest’s second-quarter revenue grew 2% year-over-year to $5.11 billion while expenses decreased 5% to $4.03 billion, producing an operating profit of $1.09 billion, up 40% over operating income of $775 million in the prior-year quarter. The airline’s second-quarter fuel expense lowered 29.5% year-over-year to $1.01 billion, representing $420 million in savings. “Second-quarter 2015 economic fuel costs were $2.02 per gallon, compared with $3.02 per gallon in second quarter 2014,” Kelly said. “Based on our existing fuel derivative contracts and market prices as of July20, 2015, we expect significant year-over-year fuel savings again in third quarter 2015, with economic fuel costs currently estimated to be approximately $2.20 per gallon, as compared with third quarter 2014’s $2.94 per gallon.”

Southwest’s half-year net profit was $1.06 billion, up 72% over net income of $617 million in the first six months of 2014, putting it well on pace to exceed its 2014 full-year record net profit of $1.14 billion.

The carrier’s second-quarter traffic increased 7.9% year-over-year to 30.86 billion RPMs on a 7% gain in capacity to 36.48 billion ASMs, producing a load factor of 84.6%, down 0.7 points. Yield lowered 5.4% to 15.72 cents.

During the second quarter, Southwest’s fleet increased by 10 aircraft to 689. The airline took delivery of six new Boeing 737-800s and five pre-owned 737-700s. It retired one 737 Classic.