Get through the turnstiles at the train terminal first and you'll be the first at security into the airport. 5 minutes to get from there to Terminal D security if you run and 5 minutes to get through there too. I did it two weeks ago in about 12 minutes and that was not particularly hurrying. I am 6-8 though and have a good stride about me. 30 minutes would be if you were in the back of each security line. 15 would be if you were in the front of each security line.