Size matters — sometimes — to Royal Caribbean International.

The Miami-based cruise line introduced the world’s largest cruise ship, Oasis of the Seas, in 2009, followed over the years by two of the same class.

But the operator achieved another milestone in late 2014 that it didn’t promote — and still doesn’t talk much about.

With the arrival of the slightly smaller but still huge Quantum of the Seas in late 2014, Royal Caribbean International became the world’s largest individual cruise line when measured by total passenger capacity.

Even though Royal Caribbean had 22 ships at the time — compared to closest rival Carnival Cruise Line’s 24 — the number of passengers it could carry surpassed any competitor. By the end of 2014, Royal Caribbean’s passenger capacity based on double occupancy in each stateroom was about 64,150, according to its annual report. Carnival’s number was 62,366.

Since then, Royal Caribbean has welcomed three more megaships, including the 4,180-passenger Ovation of the Seas in April and 5,479-passenger Harmony of the Seas earlier this month. In that time, Carnival has only added Carnival Vista, a 3,954-passenger ship that was delivered in April.

As of this month, the two lines have the same number of ships: 25. According to regulatory filings, Royal Caribbean’s capacity is now about 77,950 compared to Carnival’s 66,320.

Back when Quantum arrived, all eyes were on the ship’s new features (simulated skydiving and bumper cars), technological feats (fast Wi-Fi and robotic bartenders), and eventual destination (China). The company didn’t point out the size milestone, and even now seems reluctant to give it much attention.

CEO Michael Bayley told Skift that the company doesn’t really track that figure, but every now and then someone will add up the number of beds and pose the question. The answer, he said, is yes — Royal Caribbean is the largest cruise line.

“It’s not really something of huge importance to us,” Bayley said. “I’m not sure it’s particularly important to our travel partners or our customers. I think people associate themselves with Royal Caribbean because of the fun innovations, the quality of the service, the experience that we deliver. I think that’s far more meaningful than telling people you’re the biggest cruise line in the world.”

Still, Royal Caribbean uses the title on its LinkedIn page and, recently, included the description in a press release about Ovation of the Seas sailing from Hong Kong later this year.

Carnival Vs. Royal Caribbean

For its part, Carnival Cruise Line claims the title using a different qualifier: “world’s largest cruise line based on passengers carried.” The line also uses the phrase “The World’s Most Popular Cruise Line” (with a registered trademark symbol).

“It is important to bear in mind that we operate a substantial number of short cruises” of three to five days, spokeswoman Jennifer de la Cruz said in an email. “In fact, about half the fleet is on short cruise itineraries. This impacts our total passenger numbers quite a bit.”

For 2015, Carnival Cruise Line carried about 4.5 million passengers. Royal Caribbean International said it carried nearly 3.9 million.

Carnival expects 2016 numbers to be slightly above 4.5 million, and 2017 even higher.

“The team of analysts who track such data tell me that we expect to remain the world’s largest cruise line based on passengers carried in 2016 and 2017 based on our understanding of Royal Caribbean’s deployment plans,” de la Cruz wrote.

She said Carnival doesn’t use either phrase — largest or most popular — in advertising, and uses “most popular” (but not largest) in marketing on a limited basis. The About Carnival page on the official website, for example, goes with “World’s Most Popular.” Public relations messaging uses both, however, “and will continue to do so as the statement continues to be valid,” she wrote.

“I would say that being able to say we are the most popular and/or world’s largest cruise line based on passengers carried is a ‘nice to have’ from a PR perspective, however given our brand name recognition — which is far and away the strongest in the industry — we are well positioned from a consumer standpoint regardless,” de la Cruz said.

Regardless of how the companies use (or don’t use) the titles, plenty of coverage reveals the lack of clarity. Cruise-focused sites and magazinesnewspapers, travel guidescity governments, and even the best in cruise coverage have used the “world’s largest” line for Carnival after it was technically no longer true — at least by the capacity measure.

Adding to the confusion: Carnival Corporation, the parent company of Carnival Cruise Line and nine other brands, is by far the world’s largest cruise ship company. Royal Caribbean Cruises — which owns Royal Caribbean International — is its closest runner up.

So sometimes “world’s largest cruise line” is used to refer to the parent company, as was the case when the Associated Press wrote a story about Carnival Corp. getting approval to sail to Cuba with its new one-ship brand Fathom, which is one of the world’s smallest cruise lines.

“There are all these nuances,” said Mike Driscoll, editor-in-chief of the industry newsletter Cruise Week.

He points out that Carnival is the largest cruise brand sailing in America, with the bulk of its capacity based in U.S. ports, which might be more important to North Americans than a line’s size across the globe. Royal Caribbean has several large ships in Asia. And to Wall Street, the size of an overall company is a better measure, given the opportunities for scale, cost savings, and other advantages.

It doesn’t surprise Driscoll that Royal Caribbean doesn’t trumpet its status at the top.

“In terms of what’s more important, the world’s largest cruise ship is probably more important because you can do things on the size of that cruise ship that actually make a difference,” he said. “They emphasize the world’s largest cruise ship. They don’t want to blur that message.”

Photo Credit: The giant Allure of the Seas meets sister Oasis of the Seas off Port Everglades. Royal Caribbean International