Why is "Supplemental air carrier" trending?

Wikipedia Overview

Supplemental air carriers, until 1955 known as irregular air carriers, and until 1946 as nonscheduled air carriers or nonskeds, were a type of United States airline from 1944 to 1978, regulated by the Civil Aeronautics Board (CAB), a now-defunct federal agency that then tightly controlled almost all US commercial air transport. From 1964 onward, these airlines were just charter carriers, but until 1964 they had limited but flexible ability to offer scheduled service, making them hybrids. In some ways they were the opposite of what the law then said an airline should be. Airlines then required CAB certification, but over 150 nonskeds exploited a loophole to simply start operating. The CAB determined where certificated carriers flew and what they charged. For the most part, irregular carriers flew where they wanted and charged what they wanted. CAB-certificated passenger carriers almost never died but over 90% of supplementals did.