Air travel, especially longer than 3-4 hours, increases the risk of a thrombosis (blood clot) in the leg veins. This is a very serious condition which can occur in healthy people at any age. The risk is increased for those with a previous blood clot, recent surgery, the pill, chronic illness and smoking. To reduce your risk:

1. Exercise regularly during the flight. Walk up the aisle every 30 minutes and do leg exercises for 3-4 minutes per hour.

2. Avoid dehydration caused by low cabin humidity. Drink lots of fluids, but avoid excessive tea, coffee and alcohol.