Your risk really comes down to likelihood of being right near someone else who has the virus – much like anywhere else you go except that in most indoor places there isn’t HEPA air filtration. Planes are probably safer, then, than bars, indoor restaurant dining, gyms, and open plan offices.
But it’s confusing to look at planes, where social distancing isn’t mandated, and hear airlines say it “isn’t possible” while restaurants are being required to do it to their own financial detriment all over the country and to wonder what’s different?