How I strategically saved 40% on Spirit's Big Front Seat upgrade

Thanks to frequent fare sales and a plethora of promotional offers, it's quite easy to find a deal on a Spirit Airlines flight.

In fact, I flew the airline's inaugural domestic flight from Miami to Newark last week, and the mid-morning Wednesday departure cost just $22.90.

Though it's a great deal on paper, Spirit, like its ultra-low-cost rivals, charges separately for all ancillary fees, including seat assignments, carry-on bags, and flight changes. These extras vary in price depending on the route, day of travel and other factors, and they don't go on sale or get discounted as flight fares do.

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That's why I was especially curious when I received an email after booking my Newark flight with the headline "you're just a few clicks away from a super comfy ride at a super comfy price."

I've recently been flying with Spirit more than ever, and have really enjoyed my flights in the airline's Big Front Seat. Each of the carrier's yellow Airbus jets is outfitted with a handful of domestic first-class recliners arranged in a 2-2 configuration, available for roughly the same cost of an extra-legroom coach seat on major network airlines.

The extra width and added legroom of the Big Front Seat make flying with Spirit so much more comfortable. This year, I've exclusively flown in the first two rows on my three Spirit flights.

However, I originally decided to forgo paying for a seat assignment on my Newark flight. After all, the flight cost just $23, and I couldn't justify paying $55 — double the flight price — for a Big Front Seat upgrade for the three-hour journey.

So, when I received the email about scoring access to a discount upfront seat, I wanted to learn more. Turns out, Spirit has contracted PlusGrade, a digital upgrade solution platform, to allow travelers to submit bids for better seats.

If Spirit can't fill its Big Front Seats at the going rate of $55, why not make some money on them instead of leaving them empty?

That's where PlusGrade comes in. The service allows flyers to make bids for either a Big Front Seat or an exit row. All these seats were vacant at the time the email came through, so I figured it couldn't hurt to give it a try.

I decided to bid the lowest possible offer, $34 or roughly 40% off the going rate, for the Big Front Seat. I was then told to expect an email between 48 hours and two hours before departure informing me of the outcome of my bid. I couldn't specify my preferred seat (the window), but I could submit separate bids for the Big Front Seat or the exit row (I only submitted for the former).

Related: Is the Spirit Airlines Big Front Seat worth it?

In the coming days, I monitored the seat map. Six of the eight Big Front Seats remained unoccupied, so I was confident about my bid, despite the fact that it was labeled as having "poor" odds of being accepted.

Had more seats been occupied, I probably would've increased my bid by a few dollars, since you can modify or cancel your bid until two days before departure.

Forty-eight hours before my flight, I hadn't heard anything from Spirit. There were still six unoccupied recliners available for sale, so I had a good feeling.

Lo and behold, I woke up the day before my flight with an email from Spirit congratulating me on the bid being accepted. I quickly refreshed my reservation to see that I was assigned seat 1C, a bulkhead aisle — my least favorite type of seat. A 30-minute call to the airline's reservation team got me moved to my preferred seat, a window in the second row.

For $34, a $21 savings compared to the going rate, I was happy with my purchase. Sure it still cost more than the flight itself, but it made my inflight experience much more pleasant.

And at $57 all-in for the flight and a first-class recliner, I'd call that a big win in my book.