because the purpose of the flight is to take the pictures, gather the data etc and payment is being made for that
One test that might be used is something like:
"If no valuable consideration had been given nor promised, would the flight still have taken place in a substantially similar way?"
If the answer is no, it would seem that valuable consideration has been given or promised in respect of the flight or the purpose of the flight.
That for me at least helps to differentiate the travel articles (answer: yes) from the flight tests (answer probably: no).