A war of words between Delta Air Lines and its "Gulf" rivals in the Middle East turned increasingly bitter this week.

The latest came Thursday after the president of Dubai-based carrier Emirates rejected an apology from Delta on comments from its CEO that appeared to associate the big Gulf carriers and the 9/11 attacks on the United States.

The increasingly volatile exchange of comments comes amid a trade dispute between U.S. airlines and the three big Gulf carriers: Emirates and Etihad of the United Arab Emirates and Qatar Airways of Qatar.

More details here.