"The traveler is running to the plane."
Translation:Yolcu uçağa koşuyor.
The emphasized information normally comes right before the verb, at least in writing. Also, yolcu is the subject and Subject-Object-Verb is the most neutral verb order in terms of emphasis and it is usually preferred in writing. Duolingo mostly uses SOV for that reason. Unfortunately, they can't accept every order variation for technical reasons, so I'd suggest trying to use SOV for the next exercises.