If you sign up through Global Entry and not through the "you've flown enough that the airline likes you" version of the program, you are far more likely to get

If you sign up through Global Entry and not through the "you've flown enough that the airline likes you" version of the program, you are far more likely to get expedited screening. You can also scan your boarding pass at home and discover whether you're getting expedited or not, so you know how early you have to be at the airport.