How often are middle seats empty in stretch seating?
 

You can purchase an extra seat. You would need to call the reservations number 801-401-9000 to book it or if you live close to an airport you can go to the counter and as many other threads here note avoid the convenience fee.

If buying the extra seat, ya probably should avoid the bulkhead row or the exit rows, as those have the immovable armrests. Much better to try to get row 2 or 3.

I've tried to quarterback the seating as well (with status you can get a free seat assignment except stretch and the free "upgrade" at the check-in window). The batting average lately hasn't been so great because they've had some rock-bottom sales lately (it's a slow period) and that has attracted a lot of late bookers, with the singletons among them not wanting to pay for a seat assignment.

So the seat map even early on the day of the flight has often had a fair number of empties showing, whereas the actual flight takes off close to 100% full. Frontier seems more willing than others to leave the sale fares up (like $40 for ATL-LAS OW on a Tuesday) and bookable on just 2 or even 1 day's notice rather than raising prices close to flight time at the risk of the seat flying empty. The latter strategy, which most airlines and I think even Spirit does, is to keep last-minute business travelers from getting a bargain. Even though ULCCs don't have very many business travelers.

My experience has been similar to RustyC's; I've had very few empty middles in stretch. My luck has been better when choosing the exit row stretch seats instead of up front, YMMV. I made a comment about this to a gate agent at RSW recently and he said it was because they move the people requiring a wheelchair into the stretch seating up front to get them on and off easier. I kind of doubt that's a Frontier policy, just the gate agents at veerrrrry wheelchair-heavy RSW adapting to move things along quickly with tight turnaround times... but who knows.

Before I'd buy a second seat I'd rather investigate if it isn't better to get First Class at a proper airline for a reasonable price. One seat width isn't exactly a lot of space either to separate from the unwashed masses on... Frontier!

I have encountered no bathing issues with my fellow Frontier pax. Yes, they are sometimes from a lower socio-economic demographic than pax on the major airlines, but they are washed. And fine.

And 50 bucks (or 150 bucks) isn't likely to get you very far to a "real" first class seat on a regular airline.

To my mind, everything has a price. Which is why I sometimes fly Frontier. But only when it is dirt cheap compared to the alternatives.

Yep. And from a city like ATL you've got neither DL nor WN matching, so Spirit (on the few routes that overlap) is the only price competitor. Though WN may be the better option still for families and anyone who needs the checked-bag allowance or who flies infrequently and will be shocked negatively by the modern-day experience.

I'm actually finding Frontier preferable to the legacies IF you have status and IF you're used to traveling light. The stretch seat is something like E+ on legacies and the full carry-on makes a big difference (much easier to pack for a standard rolling bag than just a rucksack, though I DID go to Cancun and Costa Rica on the latter).

And...here's the rub...if you're flying someone like AA and in Zone 6 (regular economy, no status), the bin situation with them is so bad that you can almost count on your carry-on bag getting force-checked. Whereas with F9 I get to be part of the pre-board and the bins don't fill out as badly anyway (because they're charging other pax, though enforcement varies).

That leaves the drink, which I DO often get (as a diet Coke) on the transcons. You can bring your own bottle and fill it post-security, I s'pose. Frontier is also the only airline I know that regularly does that announcement about you not being able to consume your own alcohol in flight (Freedom! USA! USA!)

It all depends of status, though, and Frontier having a status that makes the flying more tolerable. Spirit doesn't have anything like that and isn't much into rewarding loyalty with anything. With the legacies I'm burdened with having caught them in a golden age (gold or higher 1992-2016 on somebody) and knowing full well how the experience has deteriorated for most pax. DL has gotten just one flight out of me (a former self-funded plat) since going revenue-based, and it was a one-way out of JFK tied in with an international flight and a throwaway of the last segment. F9 awards or WN are the leading candidates for positioning flights for international trips where I need to check bags.