National is offering Executive Status in their Emerald Club as a complimentary benefit to American Express Platinum cardmembers. I happen to have the card, but the link alone is sufficient, they didn’t even request the Platinum card number anywhere during the enrollment process which suggests that the offer could likely be used by anyone.
If you’re not already an Emerald Club member the offer provides free signup. And if you are it’ll provide the status upgrade.
Emerald Status members earn a free rental day for every six credits instead of seven, and choose a car from the Executive Selection rather than the standard Emerald Aisle, and when reserving a higher class of car than midsize pay for one car class below what was reserved.
(The Avis Presidents Club offer for Continental Presidential Plus Mastercard holders still appears to allow anyone to sign up, though occasionally Avis has been known to run the Presidents Club list against cardholders and downgrade member status for those without the card.)