This 15% off code on TAP is a pretty crazy deal, considering many of their fares are already some of the most competitive from the US to Europe. Moreover, you're covered by their flexible booking policy with a free change, so if you think you'll be headed across the Atlantic before April 2021, this is the deal for you.
15% Off TAP Air Portugal Flights Timeframe: 13. Aug. 2020 - 31. Mar. 2021
To book you'll need to use code "MULTI15" on the TAP website — it's also important to keep in mind that "discount" fares are not eligible, though most business class fares are. Here's an example booking: