From Delights of Learning Turkish, the present continuous tense is used: 1) to describe an action going on now 2) an action happening around now but not necessarily at the moment 3) habits / everyday actions 4) future actions 5) an action that began at a certain time and is still ongoing. So... Turkish uses present continuous even more than in English!
"Uçakla İspanya'ya uçuyoruz." Translation: We are flying to Spain by plane.
Wrong answer: We are flying to Spain.
I have made a mistake as the Turkish question does say "Uçakla" - by plane & "uçuyoruz" - we are flying.
Devil's in the detail & my English translation answer is wrong.
I cannot explain why your answer was declined by Duo?
I believe your answer to be accurate as I cannot distinguish a significant difference between flying by "plane" & "airplane." Please submit your answer as - "My answer should be accepted" using the report facility.