[![11-oxabicyclo(4.4.1)undeca-1,3,5,7,9-pentaene][1]][1]

I have been told by my instructors that for a compound to be aromatic, it must be planar. In this given molecule the oxygen seems to be out of the plane of the conjugated system: how can it still be aromatic, then?


  [1]: https://i.sstatic.net/vYeY9.png