In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.
Q: After the first 707 was made in 1957 , the Dash 80 was changed into a test planes for other things .
A: 
After the arrival of the first production 707 in 1957 the Dash 80 was adapted into a general experimental aircraft and used by Boeing to test a variety of new technologies and systems .