Airplane geek moment for which I apologize in advance:

[GEEK]

When you see the engines with the grouping of small exhaust pipes you are looking at Rolls Royce Conway turbofans, which denote a variant of the 707 called the 707-420. This was actually a later variant of the airplane, first delivered in 1960, and comparatively rare; only 37 were built. BOAC requested the -420 variant from Boeing (presumably to throw a UK engine manufacturer the business). But Pan Am and others did take delivery of some. They would have joined the fleet new in 1963 as depicted in the TV program.

Most Pan Am 707s were 707-320/B/C variants which came with Pratt & Whitney JT3D engines that did not have the little exhaust pipes. But I guess the show's producers thought -- correctly -- that the RR turbofan engines look cooler. They are taking a liberty when they make the whole PA fleet out to be -420s, but perhaps they have just one master CGI airplane to work with.

Here's a more common 707-320 with the Pratt engines:

http://www.airplanemart.com/aircraft...al-Airline.jpg

Here's a less common 707-420 with the RR engines:

http://www.airlinercafe.com/aviation...e/image032.jpg

[/GEEK]

Sorry about that.