How do I pay for flights using the Cash App? · 1. Make sure you have the details of your Cash Card to use on Alternative Airlines or any other online store. · 2. After reading this post, one can easily get his card delivered to his doorstep. So, let's start with the. Cash App is the easiest way to send, spend, save, and invest your money. It's the SAFE, FAST, and FREE mobile banking* app. *Cash App is a financial.