Facebook plane reaction arrives – but it is a secret that nobody should have seen

The cute little drawing appears to have accidentally made its way out into the wild

An Airbus A400M military plane flies before landing as a man gives a thumbs-up sign during a test flight at the airport of the Andalusian capital of Seville May 12, 2015 (REUTERSREUTERS/Marcelo del Pozo)

Facebook appears to have added a new reaction – entirely by accident.

Select people on the site were able to react to posts with a drawing of a plane, in addition to the more traditional faces.

Only some people were able to use the plane reaction – and it wasn't clear how they were chosen, apart from the fact they were on the Android app. Some found that it only appeared if they flushed the cache in the app, or shut it and re-opened it.

But everyone could see the reaction, if someone else had posted it. That led to a whole host of confusion as people tried to work out where it had come from.

As it turns out, the plane appears to have been designed as part of an event at Facebook's headquarters and added into the main version of the app by accident. It's not clear if it suggests that similar features will be coming.

It has also not been announced how long the plane will be hanging around, or whether it will come back.

Facebook first introduced reactions as part of its response to people's calls for an "dislike" button. It has purposefully added temporary new ones over time – marking events like Hallowe'en with fitting drawings.