UFO Slice

This object was filmed during a family day out and what an amazing catch.. While filming the plane flying over head this oval shaped object was spotted flying closely above the plane. This is my opinion: I don't think this is a drone as how high it is and how close it is to the plane but what do you guys think?
Source footage: Franciele Fabiana Rodrigues de Souza Oliveira
https://www.youtube.com/watch?v=v7wgnJ3GuM0
Music Credit: Infinito by Mattia Turzo
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