There is a fourth tier named Platinum and requires 150,000 tier miles. There is an additional membership known as Invitation Only or "IO" where you must be invited to this small group of members. The benefits provided are over and above the Platinum benefits.
There is a higher-tier designation known as Platinum, requiring 150,000 tier miles. There’s also a limited-access membership referred to as Invitation Only or "IO," which necessitates being invited into this exclusive group of members. The benefits provided are more extensive than those available through the Platinum level.