After spending the past couple of years reunderwriting its book of business, American International Group Inc. will embark on a program to overhaul its infrastructure and processes, CEO Brian Duperreault said Thursday as the insurer detailed improved results for the 2019 second quarter.

Labeled AIG 200 — AIG traces its origins back 100 years — the initiative will be headed by Peter Zaffino, CEO of general insurance and global chief operating officer, and will be a “three-plus year program,” Mr. Duperreault said.

AIG has transformed much of business, he said, but “the one thing we’ve never been noted for is operational excellence … we’ve legacy processes, too many manual interventions, on and on and on, and it is a drag on our performance,” he said on a conference call with analysts.

“AIG 200 will focus on opportunities to improve our core processes and infrastructure. If we are to become a top-performing company, we must make transformative and sustainable improvements that will require investment,” Mr. Duperreault said.

Meanwhile, the insurer, which has undergone a significant retrenchment over the past two years — reunderwriting much of its property/casualty book, lowering limits, cutting back in various lines, restructuring its reinsurance purchasing and installing new management — reported a hike in profit late Wednesday.

AIG reported a second-quarter 2019 profit of $1.1 billion, a 17.6% increase over the same period last year. The insurer reported a 19.4% rise in net investment income to $3.74 billion for the second quarter, but also reported a second consecutive quarter of underwriting profit following two years of underwriting losses. The combined ratio for its property/casualty operations was 97.8% for the second quarter, an improvement from the 101.3% is reported in the same period last year.

Net premiums written were down 5.7% compared with last year’s second quarter to $6.58 billion, AIG reported.

In North America commercial lines, AIG reported $2.36 billion in net premium written in the 2019 second quarter, a 1.9% increase over the same period last year. The combined ratio for North America commercial lines was 101.5%, an improvement from the 104.4% reported last year.

International commercial property/casualty net premium written fell 4.7% to $1.52 billion, and the division’s combined ratio improved to 96.8% from 104.5% in the 2018 second quarter.

The improved results reflect “a change in business mix and continued reduction in lines where we are not achieving our targeted returns,” said Mr. Zaffino. AIG is seeing reduced volatility due to better underwriting, an improved reinsurance program and better loss experience in areas such as commercial property, among other things, he said.

The insurer has also seen rate increases across much of its book, he said. Overall, insurance rates increased in the “high single digits” compared with “mid-single digit” increases in the first quarter of 2019, Mr. Zaffino said.

AIG has seen significant improvements in its Lexington Insurance Co. unit, which was relaunched as its principal excess and surplus lines unit in 2017. The business saw rate increases in “the mid-to-high teens” for property/casualty business. “Property submissions were up over 35% year-over-year, and in casualty the increase was almost 75% since the second quarter of 2018,” Mr. Zaffino said.