DVT in major vein right below knee

Patient: My dad has a DVt in leg below the knee. He was hospitalized for 2 days on I. Iv (heparin). Sent home taking twice daily shots of lo?. and Coumadin. He just has his med upped today. It has only been 3 days and he plans on flying to Jamaica feb. 11. Is this safe?. He is 60 .