WASHINGTON, Sept 9 (Reuters) - United Airlines

Chief Executive Scott Kirby said on Tuesday that the business

model of ultra-low-cost airlines is not viable.

The comments came after no-frills pioneer Spirit Airlines

filed for bankruptcy protection last month for the second time

in a year after a previous reorganization failed to put it on

firmer financial footing.

"ULCC model was an interesting experiment, consumers voted

and it failed," Kirby told the U.S. Chamber of Commerce's Global

Aerospace Summit in Washington. "I don't think the ULCC model is

viable."