There wasn’t a dry eye in the house yesterday when “Up In the Air” writer/director Jason Reitman gave an impromptu speech honoring his dad — the film’s producer, Ivan Reitman. The legendary elder Reitman understood when his son dropped out of medical school and passed on opening a sandwich shop. “He encouraged me to be a storyteller,” Jason related at a luncheon for media swells at ’21.’ Jason mused, “What parent tells their kid not to be a doctor?” Then came the killer accolade. Despite multiple Golden Globe nominations and likely Oscar gold, the younger Reitman said his proudest moment in the movie comes when the screen says, “Produced by Ivan Reitman.” Witnessing the heartfelt moment were Arianna Huffington, Gayle King, Campbell Brown, Sidney Lumet, Dan Abrams and Forbes Media Critic Bill McCuddy.