It all depends on their post op condition. Most airlines will allow travel 10 days post event (sometimes earlier with a medical certificate) Ideally I would recommend at least 6 to 8 weeks after surgery so the person feels well enough to enjoy the holiday. The British Heart Foundation state that if a person can walk comfortably for 100 yrds on the flat without angina
or undue breathlessness, then they are fit to fly. For bypass patients they can wear the circulation stockings, although the risk of DVT is reduced for anyone by keeping active on the flight and drinking plenty of non-alcoholic fluid. The most important factor for anybody going on holiday abroad with ANY chronic condition is ensuring you have VALID travel insurance. Alll medical conditions must be declared otherwise the insurance would not pay out for any claims you may make. Yes, it might mean a few extra pounds on the premium, but it could save thousands if anything happens.