A man, woman and their service dog used the emergency slide to slip out of an airplane that was preparing to take off from LaGuardia Airport on Monday morning. The passengers opened a cabin door, activating the slide, and took off as the Delta flight bound for Atlanta, Ga., was taxiing out of the runway at around 10:55 a.m., according to law enforcement sources and an airline spokesman. Antonio Murdock, 31, told Port Authority cops that his post-traumatic stress disorder was triggered on the plane, the sources said.