Hello there I have read through your question and understand your concern. In a patient with varicose veins the flying specially long hour flight s do hold some risks reason being the following- 1. Prolonged immobilisation- As you know a patient with varicose veins should not remain in one position for two long. 2. Reduced air pressure- The low airpressure in flights decreases the oxygen consumption and thus increase s the risk of embolism. 3. Stress - Stress can be another cause of increasing the risk of embolism. But by following a few instructions can reduce the risk factors considerably. They are 1. Wear compression stockings. 2. Try to get a seat with more leg space so that she can exercise her legs occasionally and maintain the blood circulation. 3. Drink lots of water to keep herself hydrated. I hope that answers your question. If you have any further questions please feel free to write. Thank you for choosing healthcare magic.