Oh, the joy of picking an airline for your travel needs! And by the look of things, you've crowned Allegiant Airline as your trusted chariot for the adventurous voyage between Billings and General Wayne A. Downing Peoria International Airport. Bravo, I must say! So, let's dive into what you can expect on this extraordinary journey.

First up, let's talk about the 'Who'. Who might be your co-fellow passengers on such a historical journey? Well, you might find yourself sharing the cabin with a delightful mix of wayward tourists, business juggernauts, and possibly a pickup band returning from a seismic gig. Doesn't that sound like the grandest party at 30,000 feet?

Moving on, 'What' exactly is Allegiant Airline offering on this voyage to make it less torturous, erm, enjoyable? If you're expecting a gold-plated seat with a personal chef at your beck and call or an open rooftop for skygazing, you might be a tad disappointed. There will be plastic meals, though! It's rather akin to a space-age culinary adventure, wouldn't you agree?

Now, 'When' should you board this airborne chariot of dreams? Allegiant is known for running sharp on time, so get ready to march onto the aircraft at the crack of dawn or during the witching hour, leaving no room for a proper bye-bye at the social gatherings you might be enjoying. So be prepared to relish the unexpected morning or midnight sprint through the airport. Naught feels more invigorating, really!

Let's also consider 'Where' you are heading. Aah yes, the magnificent General Wayne A. Downing Peoria International Airport. A place where flat cornfields meet a cocktail of minivans and over enthusiastic ‘Welcome to Peoria’ banners. Nothing screams echelons of world travel quite like Peoria. Why, it would not be an overstatement to refer to it as the Paris of the Midwest. Well, maybe that's a slight exaggeration, but who's checking?

Finally, let's address the biggie: 'Why'. Why, oh why, would one choose Allegiant for such a historic trajectory? Perhaps you're a glutton for air-ventured thrills, or just a sentient being who savors the idea of surviving airborne ordeals. One might argue the joy of journeying with Allegiant lies in the sheer unpredictability; a life lesson delivered at high altitudes. After all, where's the fun in predictability, right?

In conclusion, you might not have signed up for a luxuriating spa experience while deciding to fly from Billings to Peoria. But remember, dear traveler, you're flexing your life’s resilience muscles, reminding yourself that you can endure just about ANYTHING. And that's a triumph worth celebrating. Here's to your swashbuckling high-sky adventure!