Strike air is supposed to find enemy and prosecute these.
Therefore, if you order a strike on plain dirt at X,Y and something is actually spotted there then they will tend to target the real target over the plain dirt. So will their friends as well ("Hey Hank, the Intel pukes were right about something for once!")
. The only unoccupied hex they will "go for" is a bridge hex.
If you simply need area fire on a hex, then the correct type is the "bomber". Bombers simply go to an X,Y somewhere in the region you specify and offload the ordnance and go home. They make no effort whatsoever to find any enemy forces, unlike strike air.
Cheers
Andy