During its fourth-quarter earnings call on Wednesday, United Airlines executives opted not to provide a cost estimate of what the partial government shutdown is costing the carrier.

"It's hard to estimate, and we want to get ourselves focused on delivering on our earnings commitment. That's the focus," United president Scott Kirby said.  

The shutdown notwithstanding, Kirby said, United's corporate bookings were up 11% on a year-over-year basis during the first full work week after the holidays, which is the busiest corporate booking week of the year. That figure is inclusive of bookings by government agencies. United maintains a hub at Washington Dulles airport, where it is by far the largest operator.

Chief operations officer Greg Hart added that though the airline has seen pockets of long lines at TSA checkpoints around the country, there has been little impact in terms of people missing flights or United having to delay flights to accommodate passengers stuck in long lines. 

United's reluctance to discuss the government closure came one day after Delta estimated a January cost of $25 million due to the shutdown. 

Delta also said that the furlough of FAA aircraft certification inspectors would delay what had been the scheduled Jan. 31 launch of its Airbus A220 fleet.

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