Carnival Cruise Line said booking activity on Aug. 15 nearly doubled the equivalent day in 2019.
Carnival attributes that boost to the line dropping its vaccination requirements and easing precruise testing requirements on Friday.
Beginning Sept. 6, unvaccinated guests can sail except on cruises to Australia or on voyages of at least 16 nights. Unvaccinated guests must produce a negative PCR or antigen test taken within three days of embarkation.
Norwegian Cruise Line Holdings CEO Frank Del Rio also noted a jump in bookings after the line abandoned its vaccination and testing requirements last week.
Several lines -- including Royal Caribbean International, Celebrity, Holland America Line and Seabourn -- have abandoned their vaccination or testing requirements since the CDC ended its Covid-19 rules in July.