Boeing must wait some more before it knows when it can deliver its first 747-8 jumbo freighter.

After the board of launch customer Cargolux of Luxembourg met Friday, the air freight carrier announced that despite "progress achieved in the negotiations over contractual issues," that nevertheless "discussions over these issues will continue over the weekend."

Cargolux announced last weekend that it had reached a tentative agreement with Boeing. The board had been expected to sign off on that deal Friday and allow the first delivery to go ahead next week.

But the schedule remains in limbo for now.

Cargolux had earlier planned to take the first two 747-8 freighter jets last month and Boeing had scheduled three days of celebratory events beginning Sept. 19. The celebrations were canceled at short notice when Cargolux rejected the aircraft "due to unresolved contractual issues."

Those issues were raised at a Cargolux board meeting on Sept. 16 by Akbar Al Baker, chief executive of Qatar Airways, which this summer had taken a 35 percent ownership stake in the Luxembourg carrier.

Qatar is known to have ordered two of the private VIP passenger versions of the 747-8, and its management had done its own negotiations over a performance shortfall in the GE engine that powers the jet.

GE concedes that its engine is 2.7 percent shy of its promise to provide 15 percent better fuel efficiency than the corresponding engine on the earlier 747-400 model. The engine-maker promises an upgrade late in 2013.

On a visit to Everett last Friday to take delivery of a 777 for Qatar, Al Baker said that in the earlier board meeting he had "strongly raised" objections to the terms that Cargolux had agreed to with respect to the fuel efficiency shortfall.

However, standing alongside Boeing commercial airplane chief Jim Albaugh, Al Baker declared the dispute resolved and said the Cargolux delivery would go ahead next week.

Cargolux's position seven days after Al Baker's statement is that it "will provide an update as soon as an agreement has been reached."

Dominic Gates: 206-464-2963 or dgates@seattletimes.com