We independently evaluate all of our recommendations. If you click on links we provide, we may receive compensation. You’ll want to add these elevated wardrobe essentials to your closet before your next trip. Credit: Travel + Leisure Sometimes getting a flight upgrade isn't about the right timing or knowing the right people. Sometimes, it's all about having the right outfit. There's one way you can score a free upgrade to first class without having to do very much, flight attendants told Who What Wear : just pick the perfect ensemble. And the good news is, you don't need to be a fashion icon to do it. While many travelers prefer to wear sweatpants and slippers (or even blankets) when they fly, these seasoned cabin crew members say that putting a little more effort into your appearance can go a long way. "When we fly, we have a strict dress code to follow. No jeans or trainers—so I always go for tight black trousers and a blazer or a dress.…