Should I wear pajamas on the plane?

No. Wear 'elevated loungewear.' You want to look put-together enough to walk through immigration without feeling like you just rolled out of bed, but comfortable enough to sleep.

How do I deal with cabin temperature changes?

Always pack a lightweight scarf or a pashmina. It acts as a blanket, a pillow, or an extra layer for your torso depending on how cold the air conditioning gets.

Packing your carry-on for a comfortable overnight flight

Prioritize a modular layering system and a dedicated 'sleep kit' to transition from airport to altitude. Pack your essentials in a small pouch that fits in the seatback pocket so you don't have to rummage through your main bag during the flight.

Adopt the '3-Layer Rule'. Wear a breathable base layer (merino wool t-shirt), a mid-layer (a zip-up hoodie or cashmere sweater), and a lightweight outer shell. This allows you to adjust quickly when the cabin temperature inevitably swings between freezing and stuffy.
Use the seatback pocket system. Pack a small 6x8 inch pouch with your 'in-flight essentials': lip balm, moisturizer, earplugs, eye mask, and a toothbrush. Keep this at the top of your bag so you can pull it out immediately and stow the rest of your luggage in the overhead bin.
Prioritize compression socks. Change into 15-20 mmHg compression socks immediately after takeoff. This prevents swelling and lowers the risk of DVT on long-haul flights. Pack them in your seatback pouch for easy access.
Choose your pants carefully. Avoid denim or restrictive trousers. Wear high-quality joggers or travel chinos with at least 3% elastane/spandex. If you are sitting for more than 6 hours, clothes with zero stretch will cause discomfort.

Should I wear pajamas on the plane?: No. Wear 'elevated loungewear.' You want to look put-together enough to walk through immigration without feeling like you just rolled out of bed, but comfortable enough to sleep.
How do I deal with cabin temperature changes?: Always pack a lightweight scarf or a pashmina. It acts as a blanket, a pillow, or an extra layer for your torso depending on how cold the air conditioning gets.