Air travel is one of the quickest ways of getting to a to a distant location. While it is convenient timewise, spending time in an airplane can be hard on one's body. Fortunately, there are simple measures that one can take to reduce the harsh effects of air travel on the body. 

General

Drink lots of water (or other non-alcoholic and non-caffeinated beverages) to avoid increased blood viscosity during air travel.

Frequent flexing of the legs (at 30-minute intervals) will help to prevent Deep vein Trombosis. Flexing the legs, standing up and walking  will help keep one's circulation going properly.

Dress comfortably. Wearing sneakers or other types of shoes that can be removed easily is very practical. Your feet are likely to swell once the plane reaches a certain altitude. Your feet will suffer less if you remove your shoes.

Jet lag

Traveling across different timezones can result in what is commonly known as 'jet lag'. Again, one can take simple measures to reduce the adverse effect that such a journey can have on the body.

Rest before your departure. If you start out your journey tired, you are more likely to end up extremely tired.

Drink lots of water on the flight. Once again, drinking water is very beneficial to all airplane passengers as it keeps one hydrated.

Once on the plane, set your watch to the timezone of your destination. This will be the start of your adjusting to the new schedule.

Once you arrive at your destination, stay on the local schedule. If it is night, sleep and stay up if you arrive during the day.

Exercise regularly in the immediate days following your arrival. In addition to restoring proper blood circulation to your muscles, this will also help to accustom your body to the new time schedule.