Originally Posted by
Wyvernfan
Sorry but I’m not an expert on these types. 300 or 399 means nothing to me I’m afraid
Rob
100, 200, 300 and 400 were the series numbers of the 707, however Boeing always referred to them as 120, 220, 320 and 420. Aircraft powered by JT-3D turbofans were 120B and 320B/C. Boeing allocated customer numbers to airlines buying its aircraft which applied to the aircraft throughout its life and which also applied to any other Boeing types the airline bought. Thus a 707-436 was built for BOAC and 36 was added to any other Boeing type bought by BOAC or its successor British Airways, hence 747-136, 737-236, 757-236 etc. 99 was the customer number for Caledonian Airways for the two 707-320Cs that they bought, hence 707-399C.