I like to err on the side of caution. If possible, I like to get to the airport about 1 and 1/2 hours in advance of my flight. There are times when I've had to stand in line to check in for upwards of 45 minutes. I especially notice longer check in times with United. I do not like having to run for anything so I get there a little early and hopefully can relax with a cup of coffee and read a good book.