In CPR, we use the head-tilt, chin-lift method to open the airway.
Place one hand on the victim’s forehead, and two fingers on the bony part of the jaw. Gently tilt the head backward. This will open the airway and lift the tongue off the back of the throat. Carefully lean over the victim and look, listen, and feel for breathing. If victim is breathing, continue monitoring until help arrives. If not, begin CPR.
If a cervical spine injury is suspected, then the modified jaw thrust would be used in place of "head-tilt, chin-lift" - the jaw thrust is a technique used on patients with a suspected spinal injury and is used on a supine patient.