a cheap inflatable pool raft (they fold up nicely and make the hard floor a lot more comfortable). Keep in mind that in some airports sleeping on the floor is a no-no.
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an alarm clock or a pen and post-it pad. If you are travelling solo, write a “Wake me at 5:00 AM” note and stick a few on and around you — it works. People will wake you.
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an airline blanket and/or pillow (borrowed - NOT STOLEN!!!).