In Hawaii, Saturday is the most popular check in day. Nearly all flights to the Midwest and east coast are red eyes, so if check out is Sunday,and you have a red eye Sunday night, you will arrive home Monday morning and want to take Monday off.
Even the flights to the west coast primarily land late in the evening 10-12 pm, making it difficult to go to work Monday. So yes, for people with a 7 day vacation, Saturday is the most popular, because every other check out day requires 8 days off from work.
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