Original: Roderick Thorp (who wrote the novel Nothing Lasts Forever upon which the first Die Hard film was based) receives credit for creating "certain original characters" although his name is misspelled onscreen as "Roderick Thorpe."
Simplified: Just before McClane was forced out, he heard that the air traffic controllers wanted to head to the Annex Skywalk, a new branch of the airport, to restore their systems.