Princess Cruises has ordered two huge new cruise ships, the largest in its history, and the first in the fleet to be powered by LNG.

The newbuild order was signed this week with Italian shipbuilder Fincantieri, and the two new ships will be delivered in late 2023 and spring 2025 from Fincantieri’s shipyard in Monfalcone, Italy.

The ships are the first Princess cruise vessels to be dual-fuel powered, with LNG (Liquefied Natural Gas) supplementing the conventional heavy fuel oil used in marine engines.

The new Princess ships are likely to be a similar design to fellow Carnival-owned Costa Cruises’ new LNG mega cruise ships, which are a similar size.

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LNG is the world’s cleanest burning fossil fuel and will significantly reduce air emissions and marine gasoil, according to Princess Cruises.

“This revolutionary platform for next-generation, LNG-powered cruise ships will introduce innovative design and leisure experiences driven by the future vacation and lifestyle trends of our guests,” said Jan Swartz, President of Princess Cruises.

The two ships will be 175,000 gross tons and will accommodate 4,300 guests (at double occupancy).

Princess Cruises did not reveal any additional details about the goliathan new cruise ships, but said announcements regarding anticipated features and amenities would be made in the near future.

The two new cruise ships join three vessels already on order for Princess at Fincantieri.

Fincantieri has been building Princess Cruise’s ships for several decades.

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It’s newest cruise ship Sky Princess, the latest in the Royal-class, is due for delivery in October, 2019, with two additional Royal-class ships scheduled to enter service in 2020 and 2022.

These two new next-generation cruise ships are also the 10th and 11th contracted LNG-based cruise ships ordered by Carnival Corporation, which owns Princess Cruises.

Carnival Corporation currently has 20 new ships under contract and scheduled for delivery between 2018 and 2025.

Sky Princess will be the latest addition to the Royal-class for Princess Cruises, due in October 2019. The new LNG cruise ships ordered this week are 40,000-gross tons larger.

Princess Cruises’ Royal-class is currently the largest in the fleet at more than 142,000-gross tons. The lead ship in the class is Royal Princess, with sister ships Regal Princess, and Majestic Princess.

Sky Princess will be the fourth addition to the class, although a further three ships are planned.

Majestic Princess was built specifically for the Chinese market, and cruised via Dubai on her way to Asia from Europe.

Cruise itineraries for Princess Cruise’s new next-generation ships have not been announced, but if either is homeported in China or Southeast Asia, it is likely that Dubai will be used as a key turnaround port on the repositioning cruise.