Holland America offers interline discounts on select sailings to Vacations To Go customers who are currently employed full-time with a domestic or international commercial passenger airline or charter airline; to flight crew employees of Federal Express and United Parcel Service (UPS); to active air-traffic controllers, Air Marshalls, FAA and TSA employees; to employees of Amadeus, Revelex, and Sabre. Retired airline employees are also eligible, including those retired from defunct airlines. The spouse, parents, parents-in-law and dependent children of an interline eligible guest qualify if the interline eligible guest is not traveling. Qualifying guests must submit a letter of employment verification, a copy of their company photo ID, or proof of flight benefits at the time of booking.