That's a big panel but not an unusual thing. Years ago at KJFK I was on the EAL ramp and looked up and across the field to see a DC-10 climbing away. Then, from its belly a large panel departed and went skimming its way down toward Jamaica Bay.
I called the tower but by then several DC-10 types had departed and they didn't know which one. Turned out to be an AA flight to KLAX,
There used to be (maybe still is) a neighborhood anti-airport group near KJFK that had a rented house and on the lawn had a display of a variety of aircraft pieces that had fallen on their neighborhood. Flap vane segments, antenna, side doors from landing gear, etc. If you don't screw or attach it right, it may come off in flight.