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Which airline was the first outside the United States to launch a new Boeing jet?
Short answer
It was Lufthansa: it signed as the Boeing 737's launch customer on 19 February 1965, with an order for 21 aircraft. That made it the first non-US airline to launch a new Boeing jet. The 737-100 entered service with the airline on 10 February 1968.

The German order that launched the program
Lufthansa became the Boeing 737's launch customer on 19 February 1965, when it signed an order for 21 aircraft. With that contract, the German airline became the first non-US carrier to launch a new Boeing jet. The program had been defined based on market research pointing to demand for a fifty-to-sixty-seat aircraft for routes of between 50 and 1,000 miles. Close collaboration between Boeing and its launch customer ended up stretching that initial 60-seat jet to a capacity of up to 100 passengers.
First flight and commercial debut
The 737-100, the family's first version, made its maiden flight in April 1967. The model entered service in February 1968. The commercial debut had a specific date: 10 February 1968, with Lufthansa.
Deliveries of that first version
Only 30 examples of that first version were built. The launch airline took most of them, with 22 deliveries. Malaysia-Singapore Airlines received five and Avianca two.
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