Amazon is selling the Sony WH-1000X M3 noise cancelling headphones for just $279.99 right now. That's good for $70 off of the regular price, however these are the refurbished models. Sony and Amazon do still offer up a warranty with the WH-1000X M3, so you're still covered if anything should go wrong.
The Sony WH-1000X M3 are heralded as the best noise cancelling headphones on the market right now, having replaced the former best pair of noise cancelling headphones. Which is a pretty big deal, considering the competition out there. But somehow, Sony was able to improve on its already really good pair of headphones.
With the WH-1000X M3, you are getting some great battery life, around 30 hours on a single charge. Meaning that they will last through a full flight, even if you are flying to the other side of the world. These are very comfortable to wear on flights. Sony also has Ambient Sound available, so you can let in some sound. Basically, if you are on a plane, you'll be able to hear the flight attendants talking to you, which is also important.
You can pick up the Sony WH-1000X M3 from Amazon for just $279.99 right now, which is a pretty good price, and one that won't last long.