The primary difference between a Companion Platinum and a standard Platinum card (usually referring to Delta SkyMiles American Express cards) lies in the benefits and fee structures associated with "Additional Cardholders." A standard Platinum Card is the primary account held by the main user, which includes the Annual Companion Certificate (a "buy one, get one" domestic round-trip ticket) awarded each year upon renewal. A "Companion Platinum" card is an additional card issued to a family member or friend on that same account. In 2026, these additional cards often have a lower or $0 annual fee and allow the secondary user to earn miles for the primary account holder. However, the secondary "Companion" cardholder does not receive their own separate annual companion certificate or the full suite of status-boosting perks (like MQD boosts) that the primary holder gets. Essentially, the "Platinum" card is the source of the high-end travel perks, while the "Companion" version is a tool for shared spending and mileage accumulation.