noise cancelling headphones - these are an absolute must! I am in love with my pair from Bose.
big bottle of H2O - after I chug water before going through security, I buy the biggest bottle of water I can find.
soothing face mask - I literally have no shame. I am the crazy lady with a face mask on mid-flight, but it makes all the difference in the world! I love the Sisley Black Rose Mask or Glossier's Moisturizing Moon Mask.
socks and sandals - scandalous, I know, but slipping off my Birkenstocks in the security line has made my life so much easier! And the socks keep my feet warm throughout the flight.