You can earn 3 TrueBlue points per dollar spent when you shop at Amazon onboard your JetBlue flights via their Fly-Fi netowrk. You need to log in to Fly-Fi using the name and email associated with your TrueBlue account, then go to Amazon.com to shop. This will not work via the Amazon mobile app but only through a web browser.
Note, there are some purchase exceptions where you will not get the 3x points like gift cards, kindle product, etc. You can view all of the purchase exceptions here.
Note, you can pay with whatever your card is that is linked to Amazon. My Amazon card is currently my Chase Freedom Unlimited. So essentially you could double dip here. If I were to shop on Amazon on my next JetBlue flight, I would earn both JetBlue points and Chase Ultimate Rewards points on my purchases.
I don’t have any JetBlue flights coming up, but I will try to remember to lay off the Amazon before my next one.