Three holer - Part I
It was in the 1950's, when Boeing was already building the 707, engineers and airline representatives realized that the design of a short to medium haul aircraft would attract many companies for their domestic network. After a few prototypes were proposed, the three-engine tail mounted model 727 was chosen as the prototype soon to become reality, it retained the exact same fuselage cross section and cockpit windows as those of the already existing 707 and it had a flight engineer's panel as well. The 727, which made its maiden flight in 1963, was launched by Eastern and United which took delivery of their first airplanes early in 1964. American also received its first 727 in 1964. Lufthansa which was the first non US customer to order the type, Pan Am, TWA and Northwest quickly followed. Early customers outside America included ANA, TAP (my parents flew on a 100 Series in 1969 when they returned home from their honeymoon in Portugal) and South African Airways. The first version was the 100 but when it was built for the airlines, until the 200 model came out, the number 1 preceding the customer number wasn't mentioned because it was at that time the only existing version of the 727. For example when American took delivery of its very first 727, it was a 727-023, not a 727-123 but that didn't last long because the 100 went out of production shortly after the 200 was introduced. Most of American 727-100's were 727-023's.
The 727-200, the stretch model, was introduced a few years later. It was fitted with a rounded jet inlet on the nmb 2 engine (instead of an oval shape like on the shorter 100) as the above picture shows, which would increase the mass flow rate into the S-duct engine intake as a greater mass of air would be sucked in.
Many major airlines began to order the 727-200, most of the orders were for major US domestic airlines such as American, Continental, Eastern, National, Northwest, TWA and United. Delta, also a major operator of the type, ordered the aircraft a little later. Delta has taken delivery of the 1000th Boeing 727 built in 1973. The 727 was going to be the best seller jet aircraft in the history of civil aviation until its little sister, the 737, went into production. Foreign carriers including Air France, Air Canada, Alitalia, Ansett, Tunis Air, TAP Air Portugal, Iberia, Lufthansa, Turkish Airlines and Olympic ordered the 727-200 in the late 1960's, scheduled to be delivered in the early 1970's. The 727 was certainly a popular aircraft at that time.