What are the symptoms of DVT?

You may get swollen, tender and painful legs, especially at the back of the knee. This is very different from the mildly swollen ankles that many people get during long-haul flights. Symptoms may develop during the flight or during the days following the flight, but often there are no symptoms at all. If a blood clot has travelled to the lungs, it can cause breathlessness and chest pain. If you develop any of these symptoms, seek medical attention immediately.