We determined the feasibility of laryngoscope-guided tracheal intubation (LG-TI) in microgravity obtained during parabolic flight and tested the hypothesis that LG-TI is similarly successful in the free-floating condition, with the patient's head gripped between the anesthesiologist's knees, as in the restrained condition, with the torso strapped to the surface. Three personnel with no experience in airway management or microgravity participated in the study. LG-TI of a sophisticated full-size manikin was attempted on seven occasions in each condition by each investigator after ground-based training. The parabolic flights, which took place in an Airbus 300 over the Atlantic Ocean, provided 23 s of microgravity. During this time, the investigator opened a box with airway equipment, performed LG-TI, and attached and held onto a self-inflating bag. The efficacy of ventilation was assessed during level flight by squeezing the bag and noting whether the manikin sensors indicated a tidal volume > or =300 mL. There were no differences in ventilation success (41% versus 33%) or time to successful insertion (both 18 s) between the free-floating and the restrained conditions. More than 90% of failures were caused by the inability to insert the tracheal tube within 23 s. There were no differences in performance among investigators. We conclude that LG-TI is feasible in microgravity obtained during parabolic flight, but the success rate is infrequent because of severe time restrictions. There were no differences in success rate between the free-floating condition, with the head gripped between the knees, and the restrained condition, with the torso strapped to the surface.