Costa offers interline discounts on select sailings to Vacations To Go customers who are employed with a domestic or international commercial passenger airline, other cruise lines, Federal Express, DHL Worldwide Express, United Parcel Service (UPS), Airline Pilots' Association (ALPA), Federal Aviation Administration (FAA), International Airlines Travel Agent Network (IATAN) or National Air Traffic Controllers Association (NATCA). Retired employees of these organizations are also eligible provided the business is still in operation. Also, an eligible guest's spouse, parents, parents-in-law and dependent children age 21 and older may book one stateroom if the interline eligible guest is not traveling. Qualifying guests must provide a photocopy of their company photo ID, at the time of booking.