Check out this graphic on drug flights from the New York Times.
A picture is worth a thousand words, especially in the Honduran case, where the 2009 coup blew open the door to more drug trafficking. The Colombia-Venezuela border is a big fat mess, and Venezuela apparently is the friendly skies. The graphic comes from this story about the flights in Venezuela.
Keep in mind the note at the top, though. 80% of drugs don't come through flights.