Take a buddy with you and play Snipperclips the whole ride. You will laugh at your mistakes with every bump of turbulence. My wife and I had a blast playing that on a long flight to Hawaii back in 2017.

I got myself one of those 3rd party Nintendo USB to HDMI hubs and bring it everywhere when I travel with my Switch as it's tiny, and incase I somehow find myself in a situation where I have access to a TV (ie hotel room) and have other people that want to play too.  Doesn't take up much space at all unlike the official dock and not as fragile. (You may also need to bring an HDMI wire).

Portable charger(s) is the #1 thing. Also a USB charging cable for the 3DS. A cheap mount may be useful https://www.amazon.com/Tryone-Gooseneck-Nintendo-Samsung-Overall/dp/B01AUQ33LG/ref=sr_1_8?crid=ME1VJAFU9NP5&keywords=switch+mount&qid=1645286844&smid=A29V4QFPJPYCZC&sprefix=switch+mount%2Caps%2C177&sr=8-8.

One or two powerbanks

Good wired headphones. I like my Skullcandy cans that I got like a decade ago.

Wireless ear buds, like AirPods, are great with the Switch in portable mode. Just flick your Bluetooth off on your phone whenever you want to use them.