It's been estimated that 25 percent of Americans are experiencing something called "Vaccine Hesitancy." In other words, one out of every four of us haven't, and aren't planning on, rushing out to get the COVID-19 vaccination.

Before you roll your eyes, I just want to go on record as saying that I'm not here to talk you into or out of anything. You want the vaccine? Go get it. You're planning on skipping the vaccination? That's your business, and not mine. I'm assuming that you're a grown-up, so you make the best call for you.

Having discovered that belittling those who choose to take a pass on the COVID-19 vaccine is probably one of the worst ways to convince someone to get vaccinated, an ongoing effort to reward, or "incentivize" those who've been vaccinated (and have proof of such) began ramping up a couple of months back, and is still adding certain perks for those who've gotten their shots.

We talked before about Krispy Kreme Doughnuts, where you'll get a free Original Glazed Doughnut at any Krispy Kreme by showing your vaccination card. As long as you've gotten at least one shot, you can get one free doughnut per day through the end of this year. There have also been offers of free beer from several breweries, food from White Castle and many other food joints, rides from Uber and Lyft, tickets from several MLB teams, even millions of dollars from lotteries in Ohio and New York.

Now, Chicago-based United Airlines has added another nudge toward getting you vaccinated. Free air travel. You remember air travel, right? I have some vague memories about upright seatbacks and tray tables. United calls this offer the Your Shot To Fly Sweepstakes.

Here's how it works, according to United's website:

MileagePlus® members who upload their vaccination card to their account by June 22 will be automatically entered for a chance to win either a roundtrip flight for two or free flights for a year to any of our destinations worldwide.

30 winners, selected randomly in June, will win a roundtrip flight for two in any class of service, anywhere United flies.

5 grand prize winners, selected randomly on July 1, will receive one year of free travel to any of our global destinations in any class of service for themselves and one companion traveling with them.

LOOK: Route 66’s quirkiest and most wonderful attractions state by state

Stacker compiled a list of 50 attractions--state by state--to see along the drive, drawing on information from historic sites, news stories, Roadside America, and the National Park Service. Keep reading to discover where travelers can get their kicks on Route 66.