Newark Liberty International Airport was ranked the worst in on-time performance of any airport in the country, according to a newly released study.

According to travel site MileCards.com, two-thirds -- or 66. 7 percent -- of flights arriving into Newark Liberty were on time from June to August during the past 10 years. That's the lowest score among the 50 busiest U.S. airports. 

Nearby airports didn’t fare much better. New York’s LaGuardia and John F. Kennedy International Airport were among the top four worst.

MileCards.com based its rankings on arrivals, time spent taxiing on runways before departing and time waiting to get to a gate once the plane lands.

Philadelphia International Airport ranked seventh with a 73 percent on-time arrival rate.

Port Authority of New York and New Jersey officials said they’re working with the Federal Aviation Administration on putting in place a new air traffic control system, known as "Next Generation Air Transportation System,” or "NexGen," to reduce delays at all Port Authority airports.

CLICK HERE to view MileCards.com’s full ranking report.