Could the Oasis and Allure be joined by not one, but three more sisters?STX France is scheduled to cut the first steel for the third Oasis-class ship being built for Royal Caribbean International in Saint Nazaire on Monday, Sept. 23.

The Oasis-class ships can handle 5,400 passengers at double-occupancy and are 225,000 tons.

According to supplier reports, a fourth Oasis order will be confirmed by next summer, to be followed by a fifth.

Royal Caribbean entered into contract with STX France for a third Oasis-class vessel last December, with an option for another ship for delivery in mid-2018.

According to Royal Caribbean Cruises’ financial filings, the December agreement was conditional, and subject to closing conditions, and became effective early in 2013.

The second newbuild option (which would be Oasis four) will expire “five days prior to the first anniversary of the effective date of the contract.”