• Mallampati score III or IV

• BMI > 40 (morbid obesity)

• Limited cervical mobility

• Limited mandibular protrusion

• Thyromental distance < 6 cm

• Mento-sternal distance < 12 cm

• Short, thick neck, dental deformities, macroglossia, facial hair

• Male sex

• History of difficult intubation

• Two or more predictors of lower complexity

• Cervical immobility

• Mouth opening < 3 cm

• Airway tumors or masses

• Craniofacial malformations

• Airway manager inexperience