...The 139 has a payload problem on a 15 minute flight?
Just to clarify, they refuel in Macau, fly to Hong Kong, wait at idle, fly back to Macau and refuel. So they are operating for about an hour between refuelling, and they carry IFR reserve fuel much of the time. But yes, I wonder if the 139 would need be at a reduced payload in summer with a liferaft.