"Frequent flier miles" don't mean a thing on any major US airlines. The only factor in how they treat you is your overall profitability, which is calculated in elite qualifying miles (EQMs). This is what determines your status and your status determines your perks. These miles come from buying high cost-per-mile tickets, i.e. a $300 SFO-LAX fare, a $20K international first class R/T from IAH to LHR, etc.