Flying may cause physical changes.

While these changes are minor annoyances to most people, they can become serious medical problems for those who have recently experienced illness, injury or surgery, says the Travel & Leisure Information Center.Since altitude shifts and decompression reduce oxygen intake and increase pressure on the walls of organs, you may want to delay air travel if:

- You've had a heart attack within the past four to six weeks;

- Are recovering from bowel, eye or cardiothoracic-surgery;

- Have epilepsy uncontrolled by medication;

- Have diverticulitis or peptic ulcers.

Be sure to check with your doctor before booking a flight.