Would the following advert be illegal currently?
What specific laws would it disobey and why?
Or would it be totally legal?
It's hardly controversial compared to i.e. Tinder adverts, or Sex in the City shows,or Hooters so my intuition would be that this advert is totally fine by law.
Would the following advert be illegal currently?
The advertisement is lawful everywhere except maybe in jurisdictions with a heavy theological/religious component. In all likelihood, an advertisement that only lists flights within the US and is directed "[t]o the guy who's got a girl in every city" is meant for the US market rather than the Haredim (in Israel) or their Islamic counterparts, let alone the Taliban.
What specific laws would it disobey and why?
In some trends of Judaism women have an obligation to cover their natural hair when in public. Likewise, women in Iran must wear a hijab. This implies that, already from the "hair" standpoint, all women in the advertisement except maybe "Your Dallas darling" would be in violation of the law. This might soon stop being the case in Iran, given the recent or ongoing protests after the morality police's killing of a woman who defied the hijab law.
Hair matter aside, models' outfit in most or all photos in the advertisement would be in violation related laws in those jurisdictions. The violations are in the sense of "indecent exposure".
Someone knowledgeable in the laws of Iran, of other orthodox Islamic countries, or of Israel's legal framework would be able to identify the specific statutes or religious-legal principles at issue. Ultimately, those prohibitions are premised on the Talmud (in the case of Judaism) and the Sharia (Islam).
The advertisement in question would be totally legal today, anywhere in the United States (apart from the fact that Delta no longer offers the prices or terms quoted which would make the ad, if printed without modification, deceptive).
