Just saw this pic yesterday taken by a friend at CGK...
We know the people around the western end of the airport are protesting against the airport (noise, or land compensation dating back 20 years), and that they have used kites on the approach paths as a sign of protests and blackmail to get some money.
So, what do you think it is? Protest? Or "a new form of targetting planes"?
A friend have hit a few of these on a 737 and on one occassion he walked to the airport security office carrying the string from the kite that was still stuck to his wings. On another occasion one was hit with a "thud"... it had a metal tube on it! Another pilot dragged one all the way to the apron, and the wooden frame was in some places 1cm thick (it was a big kite though).
When visibility is good, you can end up playing dodgems/"it"/"tag" with these things on approach... or just, like some JAL crew did, mow a few of them down.
Security's been chasing these kites around, but when fighting a populace, it can be a loosing battle.