Noise canceling headphone make my ears feel like they want to bleed if I wear them too long. I use foam ear plugs when I'm sleeping.

Xanex is awesome though only for really long flights. We've all heard of Ambien on planes stories though this is another option for most people.

Keep hydrated with water, planes really dry you out. Peeing is good because blood cots from long flights are a real thing.

Please wear socks if your going to take your shoes off.

Definitely dress in layers.

Portable battery is worth its weight as is a charger which works most of the time.

Instant ramen in a styrofoam cup for domestic flights (they feed you on international flights). Slim jim, beef jerky, nuts, potato chips are other favorites of mine for domestic flights even if I don't eat these often on a normal day.