At the time Saigon was tense because Ban Me Thuot had fallen and the NVA roared down Route One toward Saigon. To anyone with the brains of a doorknob, the American adventure in Vietnam was coming to an end, but the embassy was studiedly unconcerned. Embassies do not have the brains of a doorknob, but are keenly aware of public relations. Acknowledging the inescapable is not their way. As usual, Washington would rather lie than breathe, and did. As in Cambodia, so in Nam, and so later in Afghanistan.
Apparently a genius at State realized that a lot of gringo expats lived in Nam—the number six thousand comes to mind, but may be wrong—and that six thousand hostages taken when Saigon fell would be bad PR. So the embassy in Kabul—Saigon, I meant to say, Saigon—quietly announced that expats could fly out on military aircraft from Ton Son Nhut. They didn’t, or at least many didn’t. The NVA continued its rush toward Saigon.