A couple of days ago, I flew United Airlines from Honolulu to Denver and Denver to cincinnati. On the first leg after about 30 minutes of flying, the jet was turned around and returned to Honolulu for maintenance. We ended up on the ground for about two and a half hours. Next, after I got to Denver, we boarded the plane and after we were on the plane we were told there was maintenance issues again and we had to wait another 45 minutes to fly out. On my end, I am suspicious that two issues on one trip are purely coincidence and are not the result of systematic problems. I will say that the actual flights were quite smooth once we got going. On the other hand, I have safety concerns about United arising out of this trip and I'm wondering what other people have experienced and what their thoughts are.