DO NOT attempt to close the door in flight unless you have a passenger in the right seat to do it [slow flight and vent window open]. Otherwise, turn up the radio volume and continue. It is safe to fly with the door ajar, abit annoying, abit wet, but not dangerous. If you're close to your destination, go for it. If not or if your passengers are nervous, land ASAP and close it. Pounding on the top of the door, with your fist, will pop it open if it's not properly latched. Done every time I lock that door. I'm always surprised when it opens --ON THE GROUND.