(1:45 p.m. EST) -- One of the first cruise destinations, the Nile River has been attracting vacationers since the 19th century, when a trip down the river was a must-do for Victorian-era travelers eager to see ancient temples and monuments.

However, travel to Egypt along its fabled waterway slowed following the Arab Spring uprisings of 2010 and subsequent terrorist attacks. Americans in particular stayed away.

Tourism in Egypt is growing again, and river cruise traffic is picking up, with several lines -- including Avalon Waterways and CroisiEurope -- recently announcing a return to the Nile in 2020.

Other companies, such as Uniworld, Viking, Scenic and Emerald Waterways have been operating there for several years or longer, and most are increasing capacity. Viking plans to add a new purpose-built ship, Viking Osiris, in 2020, and AmaWaterways is following suit with a vessel set to debut in 2021.

A solid percentage of the travelers are Americans, but numbers vary between cruise lines. For example, Viking Ra has been fully booked since debuting in 2018, and a large majority of the passengers are from the United States and Canada, followed by the UK, Australia and New Zealand, a company spokesman said.

Emerald told Cruise Critic that, for 2020 and 2021, the US market makes up about 25 percent of global sales, behind only Australia. CrosiEurope says when it returns to the Nile in February it expects about 10 percent of its passengers will be from the United States, with the remainder being its typical mix of French, UK residents, Germans and Canadians.

Patricia Schultz, author of the best-seller, "1,000 Places to See Before You Die," says a Nile cruise has a deep appeal to travelers.

"For generations, it's been on everyone's bucket list -- before a bucket list was even a concept," she said. "There's no place like it on the planet, and a cruise lets travelers enjoy the magnificent sites of Upper Egypt in style and comfort."

Although vacationers have been coming back to Egypt in larger numbers over the last several years, safety remains a top concern for lines.

"We made the decision to return to Egypt after review of the government travel advisories from the markets in which we sell," said Pam Hoffee, managing director of Avalon Waterways. "The United States State Department has given Egypt a rating of Level 2 (exercise increased caution). That rating is equal to that of most countries throughout Europe. We also regularly monitor the health, safety and security plans of our hotel, ship and ground transportation partners."

Other lines say they follow a similar comprehensive approach to security. "Procedures and protocols are reviewed regularly to ensure best established practices are in place," said Ellen Bettridge, CEO of Uniworld, which has been operating a Nile ship since 2009.

And travelers are getting the message.

AmaWaterways' passengers are eager to experience the river, co-owner Kristin Karst said at an industry conference last month.

"I know there are still customers who say they are not yet ready for the Nile, but there are other customers who are," she said.