United travelers flying in and out of the Denver International Airport Friday again faced travel disruptions, with 24 delays and 57 cancellations by 6:30 a.m., according to the FlightAware tracking service. United Airlines led the charge, accounting for the bulk of flight problems: 57 cancellations and 23 delays. The delays Friday pushed United Airlines’ total at DIA over six days, starting Sunday, to nearly 700 cancellations and more than 1,400 delays, the FlightAware data shows. Travelers continued to struggle with being stranded at DIA and other airports nationwide. On Monday, United Airlines staffers set up 500 cots for stranded passengers, relying on DIA officials to provide blankets for passengers stuck overnight.