Some have given a fatwa that those coming for Hajj by air assume ihram from Jeddah, while others reject it. So what is correct concerning this issue?

All pilgrims coming by air, sea and land must assume ihram from the miiqaat over which they pass, whether by land, sea or air, due to the saying of the Prophet ﷺ when he specified the miiqaats: "They are for those who come from them and others coming from beyond them who intend Hajj or Umrah (Narrated by Al-Bukhari and Muslim)"
Jeddah, however, is not a miiqaat for those coming in; it is miiqaat for its residents and for whoever has entered it without the intention of Hajj or Umrah but later decides to perform either of them from there.