SEATTLE/PARIS (Reuters) - Boeing Co BA.N bounced back from a production snarl to deliver 48 single-aisle 737s in August and extended its lead over rival Airbus AIR.PA for new orders.

The Boeing logo is pictured at the Latin American Business Aviation Conference & Exhibition fair (LABACE) at Congonhas Airport in Sao Paulo, Brazil August 14, 2018. REUTERS/Paulo Whitaker

Boeing’s August 737 deliveries, announced on Tuesday, were an improvement from the 29 delivered in July, which was one of its lowest monthly tallies in years, due to ongoing supplier delays that caused unfinished aircraft to pile up at its Renton, Washington plant.

The world’s biggest planemaker said it was making “good progress” toward fixing the logjam by year end.

Boeing's 737 and Airbus' AIR.PA A320 family of single-aisle jetliners are each aircraft makers' cash cows, and deliveries translate into big payments from airlines.

Boeing also said its 2018 net orders totaled 581 aircraft through August, up from 487 toward the end of July. That includes 90 orders in August for 737 variants from leasing firms and unidentified customers.

Industry sources said many of those orders confirmed business unveiled at the Farnborough Airshow in July.

Airbus has been slower to confirm such orders than in the previous two years, when most air show business had been formalized by the end of August. Airbus this week posted 219 net orders for January to August, including five in August.

It had announced firm orders for 145 aircraft at Farnborough, including some in its books before the event took place, leaving around 90 orders still to reach its books.

Airbus said some orders were in the process of being audited and warned against reading too much into the pace of bookings.

“One month is not representative of the entire year, especially August,” a spokesman said, referring to the summer slowdown in European business.

But the gap raised fresh questions over a landmark order for34 extra A330neo wide-body aircraft from AirAsia AIRA.KL. The Farnborough deal had brought the group's A330neo order to 100and was seen as key to shoring up the slow-selling model.

It came after a struggle between Airbus and Boeing overlong-haul carrier AirAsia X, part of Malaysia's AirAsiaAIRA.KL, Airbus's largest Asian customer. [L8N1UF4RI]

In July, Airbus called that deal “firm,” which observers say usually means approvals have been received and deposits paid. But two industry sources said details had yet to be resolved.

Industry publication CAPA reported last week that AirAsia X could switch 40 of its A330neo orders to the smaller A321neo,effectively cancelling out the Farnborough announcement.

AirAsia was not available to comment. Airbus declined comment on individual deals.