. in the fourth quarter of 2010 , the company performed its annual impairment testing on international slots and routes , at which time the net carrying value was reassessed for recoverability . it was determined through this annual impairment testing that the fair value of certain international routes in latin america was less than the carrying value . thus , the company incurred an impairment charge of $ 28 million to write down the values of these and certain other slots and routes