I can't read the article as it is behind a paywall. However as a pilot I can tell you that you are generally meant to turn off your transponder while taxiing on

I can't read the article as it is behind a paywall. However as a pilot I can tell you that you are generally meant to turn off your transponder while taxiing on the ground. Also you shouldn't turn it on until you actually have a transponder code, as you'll be transmitting an invalid code (possibly conflicting with another flight). Perhaps airliners should be made so that you can't turn off the transponder while in the air. Also, we don't know if they did actually turn off the transponder or not.