Air travel

[1] Use of air travel began vastly increasing in the 1930s: the number of Americans flying went from about 6,000 in 1930 to 450,000 by 1934 and to 1.2 million by 1938.

The point-to-point model, often used by low-cost carriers such as Southwest,[4] relies on scheduling flights directly between destination airports.

The spoke-and-hub model, used by carriers such as American[5] and Delta,[6] relies on scheduling flights to and from hub airports.

[7] Modern aircraft consume less fuel per person and mile traveled than cars when fully booked.

[15] Deep vein thrombosis (DVT) is the third-most common vascular disease, next to stroke and heart attack.

[17] During flight, the aircraft cabin pressure is usually maintained at the equivalent of 6,000–8,000 ft (1,800–2,400 m) above sea level.

Aircraft cabin air is typically dry, usually 10%–20% humidity, which can cause dryness of the mucous membranes of the eyes and airways.