We travelled during the Christmas New Year period on Qantas flying between Brisbane and Mackay on Boeing 737-800 aircraft. Our first flight Bris-Mackay on 20 December. Our flight was about to touch down in Mackay when an annoucement was made that we would be turning around and returning to Brisbane due to a warning light being activated and no engineer in Mackay. So back to Brisbane and a long wait there while it was sorted and the aircraft was refuelled. This resulted in a 5 hour trip in total. Then on 30th December we were flying from Mackay to Brisbane on a Boeing 737-800 due to depart at 6am. A mechanical issue arose and they had to fly an engineer from Brisbane to Mackay to repair the radio. He had to fly with Virgin Airlines to get there. This was a seven hour delay sitting in Mackay airport with very little information provided by ground staff who made themselves scarce when anyone dared to enquire what was going on. The departure time was changed several times. No one was available to help people who had connecting flights. People were having to phone Qantas to get new flights. I did get a text message from Qantas that said I could ask for compensation and after some searching on the website found where I could lodge a complaint. Qantas did respond very quickly, early the next day they wrote and said as a goodwill gesture I would be credited with 8000 FF points. Those points are not yet showing on FF account. Other, more regular passengers on that route told us it happens frequently that engineers have to be flown in. Surely, they can have an engineer base in Mackay. It's unacceptable to turn flights around or have passengers wait it out in a small airport for seven hours for an engineer.