Two of Qantas'747s had to divert for fuel this week. Image:YSSYGuy

Qantas has diverted its QF8 flight from Dallas-Fort Worth to Sydney via Brisbane for fuel again this week -- twice! -- because the Boeing 747-400ER plane used to fly the route couldn't reach Australia with even a reduced load of passengers.

On Sunday July 17 QF8 diverted via Noumea in New Caledonia, refuelled and arrived late into Brisbane and Sydney, delaying passengers and missing onward connections.

A different 747 diverted on Monday July 18's QF8 flight, to a different airport: this time, Auckland Airport in New Zealand.

(With timezones and the international date line, those flights left Dallas on Friday and Saturday, respectively.)

After a rocky first week in May, it appeared that Qantas had sorted out the problems with QF8, which included deciding to leave thousands of kilos of passengers' luggage behind in Dallas and diverting to New Caledonia for fuel.

But the latest diversions mean that our advice to fly to Los Angeles on the more comfortable A380 and connect from there has to remain in place.

If you are travelling in business class on QF7 to Dallas or QF8 back to Australia, make sure you check out our advice on picking the best seat available on those flights: you may be sitting in it for hours longer than the nineteen-hour-plus flight from Dallas to Brisbane to Sydney.

The 747-400ER planes that operate Qantas' Dallas flights only have the first-generation Skybed, which reclines to an angle rather than being fully flat like the second-generation Skybed on the Airbus A380. So it's important to pick a good one for as comfortable a flight as possible.

Qantas is apparently planning to refit its 747-400ER fleet with the new Skybeds, but one of the planes has just come out of an intensive two-month overhaul (called a "D-check" in aviation circles) at Avalon Airport in Geelong, and the new seats haven't been installed.