The 75,000 AAdvantage miles signup offer for the Citi AAdvantage Executive card was supposed to have expired as of October 26, 2015. However, via ChetHazelEyes on reddit, the old application link for the 75,000 miles offer still works.
As a reminder, the minimum spending on this card is $7,500 within 3 months to get the bonus. The annual fee is $450, but if you cancel within 45 days or so, you can get the annual fee refunded. The miles won’t be clawed back as long as they have posted to your AAdvantage account.