Americans travelling on small aircraft will be asked to weigh themselves as well as their luggage for the next month in response to concerns that the nation's growing girth may be jeopardising air safety.
The Federal Aviation Authority has ordered that passengers on small planes carrying between 10 and 19 people should be weighed in order to test whether the average weights the industry applies are still correct.
The FAA assumes that fully dressed adults weigh 82kg (12st 12lb) in summer and 84kg (13st 3lb) in winter - a figure that includes 9kg (1st 6lb) carry-on luggage and takes account of heavier clothing in winter. Children aged between two and 12 are assumed to weigh 36kg (5st 10lb) all year round.
But those assumptions were last revised eight years ago, and Americans have become significantly larger since then, with obesity among adults increasing by 60% over the course of the 90s.
Between 1999 and 2000 the number of obese children and teenagers grew by around 15%.
Travellers will be asked their weight or told to step on a set of scales. Given the likelihood that people will lie about their weight, airlines will add 4.5kg (10lb) to whatever figure they are told: "They usually lie in the single digits," said Peggy Gilligan, the director of flight standards at the FAA.
Airlines could be forced to leave some larger passengers or baggage behind if the studies indicate that average passenger weights have increased substantially.
On larger aircraft such differences would be of minimal importance but heavy people on light planes can make a crucial difference.
Investigators from the FAA believe that flawed weight estimates could have contributed to a crash in Charlotte, North Carolina, earlier this month which killed all 21 people on board.
The plane's flight data recorder showed that the aircraft suddenly started to rise at an angle of 52 degrees at take-off before crashing. They are examining whether an overload in the rear caused its nose to rise dramatically as the plane left the ground.
Soon after the crash, investigators asked airport staff if there had been any "large-statured people" among the passengers.
