Weighed down by rising fuel costs and the absence of one-off gains, Singapore Airlines' (SIA) first-quarter performance missed analysts' expectations.

Net profit for the first quarter ended June 30 fell to $139.6 million from a restated $337.9 million a year ago as the average jet fuel price spiked by nearly 40 per cent.

Stripping out the one-off items in the prior year, net profit would have fallen by 27.5 per cent, or $53 million, the airline said.

Revenue for the three months ended 30 June was nearly flat at $3.84 billion, versus $3.86 billion a year ago, as the growth in passenger and cargo revenue more or less outweighed the absence of non-recurring items. Earnings per share worked out to 11.8 Singapore cents, down from 28.6 cents a year ago.

"Passenger traffic is expected to grow in the coming months, although competition in key operating markets persists," said SIA. "Costs remain under pressure, especially from higher fuel prices. Cargo demand in the near term is steady despite concerns over global trade tensions, the escalation of which could potentially have a longer-term impact on air cargo demand."

Operating profit nosedived to $193.1 million, down by more than half of the $404.6 million previously, as net fuel costs rose by $154 million. Fuel costs before hedging actually rose by $312 million, but half of this increase was mitigated by hedging gains.

In fact, SIA's cargo yields rose 9.9 per cent, bucking the trend, while its passenger airlines posted declining yields. At the parent airline, yields dipped by 1 per cent, while SilkAir's and Scoot's yields slid by 10.3 per cent and 1.8 per cent respectively.

Operating profit for the parent airline roughly halved from $370 million to $181 million in the absence of one-off items, while regional wing SilkAir registered a marginal profit of $200,000 owing to higher expenses.

Meanwhile, budget carrier Scoot saw its operating profit shrink from $3 million to $1 million due to increased costs, and SIA Engineering's profit fell from $19 million to $10 million owing to lower revenue from airframe and fleet management activities.

Singapore's flag carrier went on to say that good progress had been made in the first year of its transformation efforts. Last year, it kicked off a three-year programme to grow revenue, enhance customer experience and improve operational efficiencies amid intensifying competition.

Shares in SIA closed at $10.80, down 14 cents, on Thursday. Its results were released after the market closed.