Pilatus Aircraft Ltd., maker of the best-selling, single-engine turboprop aircraft in the world, on Tuesday reported slightly weaker sales and profit for 2015 but a huge jump in customer orders.

The Swiss-based manufacturer booked sales last year of 1.12 billion Swiss francs ($1.17 billion), down modestly from 1.17 billion Swiss francs in 2014. However, the results marked the third time yearly sales topped 1 billion Swiss francs.

Operating income slipped last year to 191 million Swiss francs from 200 million Swiss francs from the previous year. Pilatus sold 121 aircraft in 2015, compared with 127 in 2014. However, orders soared to 1,367 last year from 561 in 2014.

The company, which is based in Stans, Switzerland, made substantial investments last year in research and development as well as infrastructure as it works toward beginning deliveries in 2017 of its first business jet, the PC-24. Those investments weighed on financial results.

Sales of its single-engine turboprop, known as the PC-12 NG, rose by four last year to 70, with 49 percent of those sales coming from North America. Since 1991, Pilatus has sold and delivered more than 1,350 PC-12 aircraft, making it the world’s best-selling such airplane.

03637fc508ced13dafa42956fb3c5639-PC-12_Roll_090316 A PC-12 NG in flight. Photo: Pilatus Aircraft Ltd.

Pilatus warned that its 2016 results may not be as strong as its 2015 results. The cost of developing the PC-24 will weigh on financial results.

“The expansion of our infrastructure to cover future requirements — the roll-out of our five-axis milling concept involving a total of seven high-performance milling machines, the surface treatment centre, the new assembly hall — it all adds up to a substantial cost: We are talking about investment in the triple digit million range,” Oscar J. Schwenk, the company’s chairman, said in a statement.

Further, deliveries related to an order from the Australian air force for 49 military training aircraft, known as the PC-21, will not be completed until 2017.