Summary:
Taking off on time is a key part of flying, but how often do you get to your destination on time?

Full article:
(CNN) -- How do the world's busiest airports rate when it comes to getting planes off the ground on time? We've taken the top 20 airports in terms of total passenger numbers and ranked them according to how often flights take-off with 15 minutes of the scheduled departure time. The figure for each airport is the percentage of flights that depart on time. Tokyo's Haneda tops the list with on average 9 out 10 flights departing on time, but don't expect to leave China's main airports on time -- they prop up the list with only 1 out of 4 flights hitting their allotted take-off slot. Read more: How airports cope with bad weather . Statistics courtesy of Flight Stats taken from airport information for 2012 .