If you’ve been waiting for the next great credit card welcome bonus, it’s time to leap. Like, now. Through Sept. 19, you can get up to 70,000 bonus Delta SkyMiles if you sign up for the right card. The details The Platinum Delta SkyMiles® Credit Card from American Express normally comes with a 35,000-mile welcome bonus,... June Casagrande is a writer at NerdWallet.