I've done the MCT turnaround and it's dead easy. However I was flying on an AA code MCT-xLHR (-LAX) and had to have the AA MCT-LHR boarding pass issued by the very nice transit people (all Omani) at MCT. They admonished me for not visiting Oman, and when I told them I'd love to but couldn't get in with all those Israeli visa stamps in my passport, she sniffed and said that was a silly rule. If only...

Fun lounge if traveling in J or F.