As a leading cause for in-flight emergencies is fainting, and that feeling faint has been linked to high altitudes and heartbeat irregularity, Eileen McNeely, from Harvard School of Public Health (Massachusetts, USA), and colleagues assessed how typical commercial air travel might affect cardiac health. The team recruited 40 men and women, average age 64 years, one-third of whom were previously diagnosed with heart disease.  The subjects were placed into a hypobaric chamber that simulated the atmospheric environment of airplane flight.  Monitoring both respiratory and heart rhythms, the team found that eight subjects with diagnosed heart disease experienced a run of two extra lower-chamber heartbeats while in flight-simulated conditions, while seven participants with diagnosed heart disease experienced a similar course of three or more erratic beats.  Based on their preliminary findings, the researchers urge further study to ascertain specific risks in both healthy travelers as well as those with heart disease.