From what I remember of my post-op instructions six years ago, flying straight after the operation was not recommended because of the risk of clots (I was also provided with the daily self-injections, don't know whether all hospitals do that).
But the doctor said I should be fine after 6 weeks. So we booked a trip for 6 weeks time, which was fantastic psychologically after all the pressure of the operation. The flights weren't an issue.