A: During the 1920s, the first laws were passed in the USA to regulate civil aviation. Of particular significance was the Air Commerce Act 1926, which required pilots and aircraft to be examined and licensed, for accidents to be properly investigated, and for the establishment of safety rules and navigation aids, under the Aeronautics Branch of the Department of Commerce.

Despite this, in 1926 and 1927 there were a total of 24 fatal commercial airline crashes, a further 16 in 1928, and 51 in 1929 (killing 61 people), which remains the worst year on record at an accident rate of about 1 for every 1,000,000 miles flown. Based on the current numbers flying, this would equate to 7,000 fatal incidents per year.

Fortunately, the fatal incident rate has continued to decline steadily ever since, and since 1997, the number of fatal air accidents has been no more than 1 for every 2,000,000,000 miles flown, making it one of the safest modes of transport.

Safety improvements have resulted from a wide variety of factors, including improved aircraft design, engineering and maintenance, and the evolution of navigation aids.