Albatross birds can soar without flapping their wings for six days. The birds put half of their brain to sleep and alternate whilst flying
The longest non-stop bird migration was Eleven Thousand five hundred Kilometers by a godwit from Alaska to New Zealand.

Satellite tracking reveals that some albatrosses fly around the entire planet in less than two months and can soar for six days without flapping their wings. They sleep on the wing, each half of the brain taking it in turns to turn off and rest.