I have a tricky question for all you experts out there. I am heading into retirement in a few years, but before I do, I am trying to make it to the next million mile tier for lifetime benefits. For purposes of boosting my mileage, only BIS miles count. No bonuses, credit cards, promotions, etc. I fly frequently for business and this is of course paid by my employer. Given my normal yearly travel, I will be short 250K - 300K in the next four years. So how best to boost the mileage? I have some flexibility and plenty of vacation days, but I want to be as efficient as possible. Longer flights with short turn arounds are fine. Complex itineraries with multiple legs and connections would be a real time sink for me. Short notice on fare availability is also ok. The best gateway cities for me are IAD, LAX, SFO. The major consideration is cost (isn't it always). All ideas are welcome!