For some cruise lines, 18 is the minimum age to travel solo, while others require solo travelers to be at least 21 years old, with some exceptions. Ahead of spring break and summer travel, here is what to know about four major cruise lines' age policies.

Carnival Cruise initiated its new age policy earlier this month, requiring people under 21 to be accompanied by someone at least a few years older when traveling. When booking a cruise this year, attendees must be 21 years old to travel alone,

Royal Caribbean and Carnival Cruise Lines will require that solo travelers be at least 21 years old or have a guardian.