Airwork Holdings, the aviation service firm, lifted first-half profit 19 percent, beating its prospectus guidance, and has raised its annual earnings forecast after revising the residual value of its Boeing 737 aircraft.

Net profit rose to $7.9 million, or 15.3 cents per share, in the six months ended Dec. 31, from $4.6 million , or 10.5 cents, a year earlier, the Auckland-based company said in a statement. That beat Airworks' December 2013 prospectus forecast for a profit of $5.9 million, and the company's board increased its interim dividend 1 cent to 8 cents per share, payable on April 10 with an April 2 record date.

Revenue advanced 6.8 percent to $70.3 million, of which sales from its helicopter unit gained 35 percent to $42.2 million, offsetting a 19 percent decline in fixed-wing sales to $28 million.

"It was a result underpinned by another strong performance from our helicopter operations, particularly the leasing operations," chairman Mike Daniel said. "It has also been very satisfying to have come through our PFI (prospective financial information) period having exceeded our targets and also to be able to give a reasonably positive outlook in terms of our full-year guidance."

Airwork raised its earnings guidance to be about $15.3 million in the year ending June 30, from a previous forecast of $14.5 million. The company said that reflected the impact of the revision of Boeing 737 aircraft residual values, which it purchased during the period.

The shares rose 2.2 percent to $3.25, and have increased 1 percent this year.