BrianG,

The 707 of the Captain Sim era could have had an INS added, but none of the 707 I flew through the early 80's had INS. It's one thing to have just one plane and add all the fancy stuff, but the airlines fly under FAA Part 121 and the cost of refitting a fleet of planes with expensive stuff like INS and going through the re-certification process would be pretty high. That's not to say it was not done, but the 707 was fast being replaced by newer planes that burned less fuel and carried more people. We had a few 727's that had GPS and a basic performance computer installed, but it was limited to just a few planes.

Lou