Braniff 707-227
You'll probably recognize this photo immediately as having been shot at Newark.   Here we see the aircraft that would later be pushed back as Flight 3 to Dallas and Houston.  It had arrived shorty before as flight 8 from DAL with a stop at Washingon Dulles.

Although it's not possible to ID this 707, it's certain that it was one of only five 707-200's ever built.  To be more specific, they were all -227s, since all were built for Braniff.  Only four ever flew in service -- the first of the series was tragically lost, along with its crew, in an acceptance / training flight accident just before it was too be delivered.

The -200 model was the "hot and high" version of the 707, having the short fuselage of the –100s and JT4A-3 engines that were used on the early –300s.  The combination of a lighter airframe and more powerful engines helped provide the required performance for Braniff's high-altitude ops out of Mexico City.

Newark, July, 1965