American Airlines has found that consumers don't always book their flights on their first visit. So the airline sends abandoned cart emails to anyone that has left the site without booking a flight that has been saved. Emails go out 24 hours after a flight was saved in the customer's cart. The email shows the lowest and most flexible flight based on the flier's cart. These emails have a 300 percent higher pen rate than standard emails and a 200 percent higher click through rate.