If you have pets (cats, ferrets), they can easily pull the drain plug out.  It’s a slip fitting.  GE should make all drain ports THREADED!  

Unbeknownst to me the air conditioner was draining directly on my carpet for several days before I noticed that the ferret or cat had pulled the plug and stashed it in their secret hiding place.

Luckily I was in the middle of replacing my carpet, and ripping it out, otherwise it might have been the entire summer before I realized the unit was draining into the carpet!!!

GE was great about customer service in shipping out a new drain plug, but the coupling should be threaded.  Duh!