For me a good eye mask is an essential sleep accessory, especially on long or overnight flights. I take one in my carry on even for short flights – I never know when I will want to catch a short nap and block out the light.
The best masks have a contoured eye cup so your eyes don’t get pressed when you have the mask on. I had one that was too flat and stiff and it was very uncomfortable.
An adjustable strap is nice, but since the straps are usually elastic and will fit most everyone that is only a consideration if you have an unusually small or large head.I also feel that having two straps helps the mask fit better, but that is personal preference.
Some of these masks include ear plugs and a carrying case, which is not necessary, but is a nice touch.
Any of these 6 eye masks should be comfortable to wear when flying:
Sleep Mask Contoured Cups and Adjustable StrapNatural Silk Sleep Mask with Contoured Cups and 2 StrapsContoured Sleep Mask with Adjustable Strap, Earplugs & PouchUltralight Contoured Eye Mask. Comes in Many Fun Colors TooContoured Sleep Mask with Ear Plugs and Carry PouchPack of 4 Contoured Sleep Masks in Black/Blue/Purple/Red