 MATS declared that in order to qualify for contracts supplemental carriers must earn at least 30% of their revenue from civilian-chartered services, a measure designed to attract only the most robust carriers.MATS soon added that only carriers flying jet aircraft could take their contracts.Within a few years, all but those in compliance with the MATS directives had fallen into bankruptcy, leaving the constricted group of some half-dozen supplemental carriers the lone progeny of the postwar non-skeds.