The Carnival Corp. Panorama cruise ship sits docked in Long Beach, California on March 7, 2020. (Patrick T. Fallon/)(Bloomberg) — Carnival Corp.’s flagship cruising brand extended its pause on U.S. departures through the end of April and shelved operations in Australia through mid-May amid lingering pandemic concerns.Carnival Cruise Line also canceled European trips on Carnival Legend that had been poised to start in May, and delayed trips on Mardi Gras from Port Canaveral, Florida, until the end of that month, according to a statement Friday.The announcement is the latest in a long line of delays since the entire industry essentially went on hold in mid-March. In the pandemic’s early days, outbreaks on ships killed customers and crew and turned some vessels into pariahs that no port would accept.With the vaccine rollout just beginning in earnest, many of the companies seem to be writing off a significant part of 2021, having raised billions of dollars in debt to keep themselves solvent. Even when they start taking customers again, Carnival Chief Executive Officer Arnold Donald has said, any resumption is likely to be gradual.Yet Carnival said earlier this month that cumulative advanced bookings for the first half of 2022 are now ahead of 2019 levels, reflecting pent-up demand.Carnival shares were down 2.8% to $20.15 at 9:44 a.m. in New York. The stock tumbled 57% last year.