Frontier Airlines is a low-cost carrier based in Denver, Colorado. It only offers economy class, and each aircraft has a different animal painted on its tail.
Here is the promo page and registration link for this offer: GET 10,000 MILES WHEN YOU FLY BEFORE DEC. 31, 2021!
This is a pretty unique promotion, so let’s take a look at the requirements below ↓
First, you need to be a Frontier Miles member.
Fill out the Bonus Miles Form online to confirm that you have been vaccinated against COVID-19 before participating in the promotion. (In practice, this is just a web form.)
Book your ticket between 8/2/2021 and 8/30/2021.
Complete your travel before 12/31/2021. (Your departure time must be at least 24 hours after registering for the promotion.)
For every two flights, you earn 10,000 miles, up to a maximum of 100,000 miles. (Both one-way and round-trip paid tickets qualify, but award tickets do not.)
According to the official description, 10,000 miles is enough for a one-way flight. I did a quick search, and that does seem to be true. See the example below ↓
But we should also look at the actual cash ticket price ↓：
The fare itself is already very cheap, so when you do the math, 1 mile is worth less than 1 cent...
Frontier is similar to Spirit. Bags cost extra, though the seats are slightly better. The seat pitch is 28-31in, while Spirit is a uniform 31in. I would not choose Frontier for flights longer than two hours, because my knees would be pressed against the seat in front of me... The seatbacks also do not recline unless you pay extra for stretch seats.
My suggestion: for flights around an hour, if the total cost comes out much, much cheaper than other airlines, then it may be worth considering.