The Swissair plane which flew the six "houseguests" from Tehran to Zurich was a DC 8-62, made by McDonnell Douglas (construction number 46134/513) and delivered to the airline in 1970. The plane was powered by four Pratt & Whitney engines (JT3D-3B).
Its registration - clearly visible in this photograph - was HB-IDL (while it was in service with Swissair). Its code name was "Aargau."
Swissair flew this plane between 1970 and 1984. It was sold, in 1984, and re-registered as N924CL, flying for Capitol Air (which became National Airlines). Later, it flew cargo for Airborne Express with registration number N802AX.
The plane is no longer in service.
Click on the image for a closer view.
Image of the plane which transported the six diplomats from Tehran to Zurich by Edvard Marmet. Copyright, Edvard Marmet, all rights reserved. Photo provided here as fair use for education purposes. Online via airliners.net.