- 'Mile runners' take trips just to get frequent flier points
- Ben Schlappig traveled 270,000 miles in four days
- Many airlines are changing their reward systems to make it harder
(CNN)It's amazing what (literal) lengths some people will go to earn frequent flier miles. Take Ben Schlappig. Over his lifetime, he's accrued about four million miles. Half of those, he estimates, were earned on "mile runs" -- trips taken for the sole purpose of earning points.