Suggest you call Avis and ask them directly. Years ago - it used to be you just walked 20 yards across the street to rent your car and it was parked behind the small counters/offices, but now - I think that's airport parking and the car lot is a 5? minute bus ride away? No idea what time the rental car lot opens but am guessing you should be able to drop off your car even if the Avis counter is not open - note the mileage and turn in the keys somewhere?

Would first drop off the luggage at the check in counters - and then go turn in the car.

Also - for Sat am departures from Lihue - wouldn't think it's that crowded at the airport - or a long security line, and the gates are close to check-in, unlike at bigger airports.

Here are a couple pics of the airport. http://hawaii.gov/lih/airport-parking and http://www.hawaiidrive-o.com/lih-kauai.html

Also - since your hotel is close to the airport - you might use their shuttle, which also guessing - would start early. You could turn your car in the day/night before (maybe save a day's rental) and use the shuttle to get back to the hotel and reserve it the next morning for your departure.

I have not been to Lihue in ten years, but everything as right there. Very easy.

I'd use the Kauai Beach Resort Shuttle and turn in my car the night before, just check to make sure their shuttle runs that early.

I don't rent with Avis, but I'm 98% sure that although there are counters outside at the airport--all actual pick ups and drop-offs are done at an off-airport location. As Tom mentioned--it's about a five minutes from the airport.

Because of the hour, I'd use the KBR shuttle the night before--and check to be sure that the KBR shuttle will run that early. Or ... be sure there is an after-hours drop off. If you need to take a taxi it couldn't be much. KBR is only a five minute drive from the airport.

FYI, in between KBR and the airport--on the main road--I saw a feral pig with a baby yesterday! Sooo cute.

I'd check with the airline, but at that hour I don't think it will take long to get through the agriculture check and security. I've seen it be a nightmare that took an hour during peak hours when more than one major airline had flights to the mainland. Although lately, it's gotten better. I'm guessing you'll breeze through in a few minutes--but again, I'd check with the airline.

Have a great time.

Call Avis LIH directly and I am %98 sure they will tell you that you will make your flight no problem, that you should drop off your companions and show up at the Avis Return a few minutes early as they are quite familiar with each and every early morning flight arriving and departing and often open their doors a bit early and will expedite your return to the terminal.

808-245-7995

Having just rented there a few weeks ago, I believe only Enterprise/National cars are located "off airport" down past Vidhina Field on Halau St in the industrial section, about a 5 min shuttle ride.

The rest have their lots on premises but since 9-11, it's still a shuttle ride/short walk thru the parking lot if you wish to stretch your legs upon arrival. But since you are leaving...

All of the check-in booths are across from the Ag Check-in/ Baggage drop off. But since you are dropping off the car, it will be at the location where the shuttle took you to get your car.

Your carry-ons help save time.

Update info.
I telephoned Avis Lihue directly. The agent told me that the airport opens at 5am and that people are there, but that they have paperwork to do and don't really have the counter open for awhile so that is why the site says open at 5:30am. The check-in traffic is light when they open, so she thought it would be fine to return an Avis car to catch 6:30am flight.

I might telephone at 5:15am next Saturday local time to see if anyone answers.

I forgot to ask whether one can walk to the terminal. She did mention starting the shuttle at the same time as the check-in desk.