Frontier is having a sale just for today. $21 flights in celebration of their 21st anniversary. Only select destinations are $21 but they have plenty of other flights for under $50 as well. Before I continue, keep in mind that Frontier is a budget airline. They will get you there in one piece, they fly modern jets, but they charge for everything.
Knowing that, they have some amazing deals if you can keep the added costs down. They charge even for a carry on bag, you are only allowed to bring a purse or suitcase for free.
From Denver there are some crazy deals going into the end of summer. These sales are only good on Tuesdays, Wednesdays, and Saturdays.
From Phoenix you can get to Houston for $59, that isn’t bad. One thing to keep in mind is you can use these flight as “positioning flights”. A positioning flight is one that gets you to an airport other than your destination in order to save you money on the connecting flight. For example, you want to go to Orlando but every flight from Phoenix into Orlando is $222 one way. Well, you could book a $59 flight to Houston and then catch a $94 flight from Houston to Orlando. (only $153 total) Mix and match to save!
Another example, you want to fly Phoenix to Bozeman, MT. The cheapest one way you can get is $110 through United with a layover. If you book a $49 Phoenix to Denver and a $21 from Denver to Bozeman, you are getting to Bozeman for $70. Don’t be afraid to book separate tickets and use connections to save you money. Just make sure to space out your flights with ample time so you don’t miss a connection, they will be less forgiving since you booked two tickets instead of one.