United Airlines CEO Scott Kirby recently visited Airbus' headquarters in Toulouse to discuss potential orders of A321neo jets from Airbus. This comes amid delays in the certification of Boeing's 737 MAX 10 aircraft, for which United has substantial orders. Any deal between United and Airbus would depend on available production slots for the in-demand A321neo. It could also involve renegotiating United's long-delayed order of 45 A350 widebody jets from Airbus.