Cryptonym: NIACT
William Atwood, The Reds and the Blacks (Harper & Row, 1967), p. 24.
William Atwood, a prominent member of JFK's administration, defines NIACT as "a telegram important enough at night to wake somebody up for".
Foreign Relations of the United States, 1961–1963, Volume XII, American Republics
"Night action", a communications indicator requiring action by the recipient at any hour day or night.
https://www.cia.gov/readingroom/docs/DOC_0000915435.pdf
05/11/54: Cable from Guatemala City to Director: Slugline RYBAT PBSUCCESS: "1. JMBLUG (John S. Peurifoy) advises he received NIACT cable from Assistant Secretary Holland ordering John Calvin Hill, Second Secretary Embassy, to report department for two weeks. 2. JMBLUG feels Holland desires Hill analyze Communist situation here and fears this indicates Holland may still desire OAS presentation. 3. Hill has certain reputation commie expertness based on report he wrote primarily containing info furnished him to great extent by this station."