Boeing Co. (BA) - Get Report  shares traded higher Tuesday after it booked $3.6 billion in new orders for its 737 MAX jet at the Dubai Airshow as the world's biggest planemaker continues to estimate a potential December return for the grounded aircraft.

Boeing said Kazakhstan-based Air Astanta plans to purchase 30 of the 737 MAX 8 planes to service its low-cost airline FlyArystan. List prices for the jets suggest an order worth around $3.6 billion, although carriers will often negotiate discounts on bulk orders that reduce the total cost. Turkey's Sunexpress, another discount European carrier, said it ordered ten MAX 8 jets yesterday at a list price of $1.2 billion.

"Air Astana has become one of the leading airlines in Central Asia with its deep focus on safety, reliability, efficiency and customer service. At Boeing, we share those same values and are honored to expand our partnership with the 737 MAX," said Boeing commercial CEO Stan Deal. "We believe the efficiency and reliability built into the 737 MAX will be a great fit for FlyArystan. We look forward to working with Peter and his team finalize an agreement that meets their fleet and operational requirements."

Boeing shares were marked 1.2% higher in early trading Tuesday to change hands at $373.74 each and have gained more than 15.3% since mid-August. 

The new orders followed Boeing's estimate of a mid-December return to service for the grounded 737 MAX last week, which was taken from the air last spring following crashes in Ethiopia and Indonesia that killed 346 people, although Deal told reporters Saturday that a firm return date was up to regulators at the Federal Aviation Administration.

"Boeing continues to target FAA certification of the MAX flight-control software updates during this quarter," the company said in a statement last week "Based on this schedule ... the resumption of MAX deliveries to airline customers could begin in December, after certification, when the FAA issues an Airworthiness Directive rescinding the grounding order."

Boeing shares have been gaining steadily since the company posted weaker-than-expected third-quarter earnings last month but said it still expected the 737 MAX aircraft to receive approval from at least one major regulator before the end of the year.

Boeing said it would increase costs related to the grounded 737 MAX by around $900 million, taking the total to around $3.6 billion, adding it not only expects a return to service in the fourth quarter, it sees production rising from 42 planes a month to 57 planes per month by the end of 2020.

Boeing said overall aircraft orders fell by more than two-thirds, to 62 units for the third quarter, and trimmed its forecast for 787 Dreamliner production to 12 planes from 14, beginning in late 2020, thanks in part to U.S.-China trade tensions.

The aerospace company still has an order backlog of $470 billion, thanks to net orders of $16 billion in the third quarter.

But the continued difficulties in sorting out safety issues with the grounded 737 tipped free cash flows into negative territory, with Boeing pegging the figure at -2.42 billion, down from +$4.56 billion for the same period last year.