(Portland, OR)  --  Portland International Airport is ranked the best airport in the U.S.  That's according to "Travel + Leisure" who named PDX the top airport for the fifth consecutive year.  Factors considered in ranking the nation's top airports include accessibility, check-in, security, restaurants and design.  "Travel + Leisure" says more than 85-percent of flights arrived and departed within 15 minutes of their scheduled time at PDX.