The ombudsman's office said the complaints came less than a month after the release of the 2012 Ryanair Cabin Crew Charity Calendar, benefiting charity DEBRA, which helps children with the genetic skin disease Epidermolysis Bullosa, The Local reported Thursday.
"People think the [calendar] is sexist and that it doesn't belong on a Web site meant to sell plane tickets," Advertising Ombudsman Elisabeth Trotzig said.
Ryanair now has two months to respond to the complaints before the ombudsman decides how to proceed with the case.
Stephen McNamara, a spokesman for the airline, said the calendars have been released every year since 2008.
"Ryanair's cabin crew calendar has raised 500,000 euros ($672,000) for charity in just five years and we will continue to support the right of our crew to take their clothes off to raise money for those who need it most," McNamara said.