First off, a hearty THANK YOU to moondog for taking the OTAQ&D baton and running with a nice set of questions that have generated a robust percolation amongst the participants. Well done!

4. Which airline was the first to introduce in-flight entertainment systems on its aircraft, and what year did it occur?

Well, I believe the first airline to show an inflight movie aboard its airplane was Alaska aboard a DC-6. I'm not sure of the year, but I'm thinking late 1950s or even 1960 since Alaska took delivery of its first jet - a Convair 880 in '61 or '62.

That said, how many airplanes were we working with here? Was it just a single DC-6? Also, I don't recall hearing that movies were continued aboard the 880s.

As such, I believe TWA would be the first carrier to introduce "in-flight entertainment systems" aboard its aircraft (plural), with that aircraft being the 707. I don't believe TWA offered movies on anything other than transcon flights, which the 880 didn't have the legs for. As to the year - early 1960s, no doubt. Let's go with 1962