US operator Norwegian Cruise Line Holdings (NCL) has pushed up fourth-quarter earnings while enjoying a record start to this year.

The company said net profit was $154.6m to 31 December, against $98.8m in 2017.

Revenue increased 10.5% to $1.4bn, compared with $1.2bn the year before, as it added another ship to the fleet.

There was also a growth in ticket prices and "robust onboard spending", it said.