I just found this on Mystic Stamp website:
On May 12, 1999, the USPS introduced a new series of Airmail stamps – the Scenic American Landscapes.
These stamps are part of the Airmail series. Airmail as its own separate service came to an end in 1977. After that time, airmail stamps were issued to pay international rates. After 1995, the USPS called these "international-rate stamps," though they still said "Airmail" on them.
Then on May 12, 1999, the USPS began a new series of Airmail stamps that would picture the "mountains, canyons, and swamps that comprise our country's diverse and majestic terrain." However, unlike previous issues, these stamps wouldn't include the word "Airmail," rather, they had a small silhouette of a jet next to the denomination. Like the stamps before them, these new issues paid the international rate. But they could also be used to pay for other postal services and make up other rates. New stamps would be issued as the rates changed. There were also postal stationary items including postal cards and aerogrammes.
So, for the bottom line, it seems they were:
International Rate Stamps, which probably transported mail in an airplane, and Scott classifies them as Air Mail, but weren't really called Air Mail.