So far, as of 6 pm (mountain time), flights will not be cancelled.
Icelandair and many European airlines are blaming an industrial action in Keflavik airport, affecting all flights departing between 10:00 and 11:00.
Icelandair has posted a travel alert, with apologies to travelers' delays. Several passengers at Denver International Airport expressed displeasure at the unforeseen delays.
Follow Mary Jeneverre on Twitter @Jeneverre.