Frontier's Economy Bundle offers a carry-on and seat choice, ideal for budget travelers.
Consider Premium Bundle for extra legroom and priority boarding at a small additional cost.

Planning a trip from Denver to Seattle? KAYAK’s data-powered insights will help you find cheap flights. Learn the best time to fly, how early to book your ticket, and other tips to secure great prices.
Based on flight data for the Denver to Seattle route, it's generally cheaper to fly on Saturdays and in the month of January. Here are some tips to help you save money when booking this route:
Cheapest Route: Stick to the direct route from Denver International to Seattle/Tacoma International for the best prices.
Booking Advance: Try to book your flight at least 21 days in advance to get the best rates.
Cheapest Airline: Consider flying with Frontier, as it generally offers the cheapest fares for this route.
Direct or Layover: It's cheaper to fly direct on this route than with a layover.
Route Selection: The direct route from Denver to Seattle is typically the cheapest option.
AI-powered; AI can make mistakes.
| Low season | January |
|---|---|
| High season | July |
| Cheapest flight | $51 |
Direct departures
Denver Intl to Seattle/Tacoma Intl
Monday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Tuesday
Alaska Airlines, Delta, Southwest, +1 more
Alaska Airlines, Delta, +2 more
1
Wednesday
Alaska Airlines, Delta, Southwest, +1 more
Alaska Airlines, Delta, +2 more
1
Thursday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Friday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Saturday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Sunday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Direct returns
Seattle/Tacoma Intl to Denver Intl
Monday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Tuesday
Alaska Airlines, Delta, Southwest, +1 more
Alaska Airlines, Delta, +2 more
1
Wednesday
Alaska Airlines, Delta, Southwest, +1 more
Alaska Airlines, Delta, +2 more
1
Thursday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Friday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Saturday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Sunday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
My first flight was delayed by over an hour, luckily I had Long layovers on an itinerary from hell, because when you book a Saver ticket, they change your itinerary and make it many stops and long layovers, and there were still delays. On the return flight there was a delay in the first leg, Orlando to Seattle, so I got up really early for nothing, and on the last leg Anchorage to Fairbanks, it was over 2 hours late taking off! I didn't get home until 1 :30am! By the time I got my luggage, the flight landed at 1 am. For the departure day, I was up from 6am to when I arrived the next day at 6am in Orlando. So I was up for 22 hours, 3:15am to almost 2 am the next day. On the return day. The moral of the story is, DON"T EVER BUY SAVER TICKETS! You can't even upgrade your seat when you do that and then at the last minute they want Big bucks to upgrade the day before leaving.
My first flight was delayed by over an hour, luckily I had Long layovers on an itinerary from hell, because when you book a Saver ticket, they change your itinerary and make it many stops and long layovers, and there were still delays. On the return flight there was a delay in the first leg, Orlando to Seattle, so I got up really early for nothing, and on the last leg Anchorage to Fairbanks, it was over 2 hours late taking off! I didn't get home until 1 :30am! By the time I got my luggage, the flight landed at 1 am. For the departure day, I was up from 6am to when I arrived the next day at 6am in Orlando. So I was up for 22 hours, 3:15am to almost 2 am the next day. On the return day. The moral of the story is, DON"T EVER BUY SAVER TICKETS! You can't even upgrade your seat when you do that and then at the last minute they want Big bucks to upgrade the day before leaving.
I had the worst seat neighbors thry literally snored so loud and the man next to me man spreaded the whole time i couldnt sleep
Service was great! 👍 Seats were small and absolutely not enough leg and feet room!!!
We sat on the tarmac for so long when we got to SeaTac that half the plane missed their connections.
Packed flight, cabin was so hot and stuffy that a woman fainted in the aisle. Crew were so inattentive that it took a awhile for just 1 Crew member to respond. Seat was incredibly cramped. Made to check bag because of "no overhead room" but there was plenty of overhead space when I was one of the last to board. Why is someone in boarding class A-D entitled to carry-on space but people in class E-F aren't? Whole flight was very uncomfortable. Shitty flight with a shitty airline. No more Alaska airlines for me.
The boarding was quick, but the cabin was uncomfortable and I got stuck in the galley while the flight attendants handed out drinks after using the lavatory.
I understand it’s their right, but when two of my party missed the flight after checking in it seemed insensitive to cancel all of their subsequent flights and for us to lose the extra seating despite having paid for it @ the very least we could’ve been refunded for the checked bags that we prepaid for and never used.
Great. Went right to the desk and the people were helpful and kind. I was able to get my boarding pass in under 5minutes. They made sure I received the text.
In evening be nice to have something sweet rather than dry pretzels
Poor, no one with Alaska Airlines is in a hurry to do anything. Slow, lack of intent, inconsistent.
Flight was late from Newark to Atlanta, I asked flight attendant to please let my family of 3 out first when we landed to Atlanta because we were late for our connecting flight to Quito. She didn't and we were late for 5 minutes we couldn't board the plane and spend hours trying to get another flight with customer service for the next day.
I really liked the legroom. I am 6’4”.a at For some reason our seats were not together and using the app to fix it didn’t work. Passengers were nice enough to move for us but you should absolutely ensure a parent sits with their child.
Late delayed flight delays boarding and delays leaving and delays on arrival too. Cramped plane no room no food.
DTW line is too long. The flights from DTW to BWI are always delayed for unknown reasons.
Delta canceled our flight and we had to scramble to find another airline to get home. Phoenix is not a delta hub so they didn’t have another plane. It would have been a red eye though Salt Lake City. Getting in at 5am. No bueno.
This flight was no comparison to our prior flight. I'm thinking it all has to do with the age of the aircraft.
This flight was a first class choice and left much to be desired. Seat backs on seats were falling apart and torn. Seats actually didn't come to a "full & upright position". Pull out table was sprung. Not any significant leg room. All in all we were on an obviously older plane and felt overcharged for what we received as first class.
Flight was delayed several times. At one point, they "pulled back" 15 minutes from the delayed boarding and sent a text saying we would board sooner than previously advised. The flight then was delayed again. And when we boarded, there was an unspecified technical issue which had us waiting in the plane for about an hour.
Delta is a good airline. I've never had an issue with Delta. I'll continue to fly with them until they show me that I shouldn't.
The only thing nice I can say is the flight crew was really nice and apologetic about the situation. They shared as much information as they had and advised us on what we could do about missing connecting flights. The boarding process was so slow. The gate agent was working by herself and should have had someone working with her. It took almost an hour to board because she was trying to board a full flight of people and provide customer service to everyone who was flying standby and/or had questions. It was really chaotic. This didn't help the fact that we were delayed and folks were missing connections the longer it took.
The crew at Hawaiian Airlines was fantastic. Kind and hard working. The pilots were great with giving us all the updates to make sure we were informed.
Very good. Nice plane and we sat in economy plus - bigger seats, more room. They served a meal and snacks, and the meal was an apple stuffed pancake that was very good! The snack for us was a hummus sandwich - also very good. The flight attendants were helpful and nice. They have plenty of movies and shows to watch. My only negative -- they changed our flights around and did not adjust the layovers, so we ended up with a very long and unnecessary layover in Honolulu.
I liked the Starlink WiFi but didn't like how they said they were the only airline to offer a free meal and it turns out to be just a standalone sandwich and then charge for snacks to go with it. Rather have the free snacks like Southwest, but have the option to purchase a decent meal for a 5+ hour flight.
Flight scheduled to take off at 5.55pm but it did not take off until 7pm due to some food delivery delay.
Unfortunately, I was put into the middle seat in the first row of premium seating. Sounds nice right? No! that is the worst seat in the plane. I wish I was in economy rather than be in that seat! There is no seat back pocket, no tray table, no charger. Nothing! so unless you're row mates are willing to let you share their basic amenities any flyer should have, you are stuck. It was the worst experience ever! And the flight attendant forgot to take my drink order. I felt like the forgotten flyer.
Delayed and cancelled flights were hard and very stressful, both ways!
The crew was quite good, they came by often with drinks or to collect trash. But what wasn't nice was the flight was over weigh and several people had to be rebooked. I was questioned whether I should have a seat when I was getting to it. The in-flight entertainment kept buffering and interrupting. And the route took the airplane through high winds which caused us a longer flight
Wasn’t on the flight due to Alaska cancellation…also after all the rerouting, I was going to be on a later flight that left SFO at 7:47pm, which meant an almost 6 hour layover. That same Hawaiian flight was delayed for another 2hours.
I had to cancel the flight because with a 3 hour delay for 'unexpected maintenance' in getting to LAX, I couldn't connect to an overseas flight that I had booked on Scandinavian Air.
The flight was CANCELED!!! Can’t get much more “poor” than that. I had to switch to American Airlines, add another layover and got home in Honolulu 4 hours later than I was supposed to be home. One bright spot was Josh with Alaska Airlines at SFO. He got me on a United Flight that got me home a few hours before I would have. Without him I would have gotten home almost 7 hours after my originally scheduled flight.
Sitting on the runway after we land for almost two hours! Not sure if we should blame United or Just Dumpy Vance.
Flight was late - I was downgraded from first class to coach
Crew seemed a bit cranky. No seatback screens. But boarding was efficient and on time and we arrived early.
See previous note about the passenger in Denver who threw my husband's bag out of the overhead bin in order to maker room for his own. And the flight attendant back up the new passenger.
Terrible. They wouldn't allow me on my flight on the 14th..
it was so bad. I tried to board my flight from vancouver to saskatoon. And to my surprise they did not board me cause the flight was changed and no email was send to me. and on my boarding pass which i got from seattle says different flight. I did not knew anyone from Vancouver, air canada crew was rude, i asked for today flight but they were rude and i had early morning dental appointment in saskatoon. I was so much in pain and my whole day is wasted today. and i suffered alot. They did provide me hotel but they did not provide me any food. I am really really disappointed first time had so bad experience with air canada. I may think twice to book it again. If i can get any reply or any composition that would be great. Thanks
Impressed with the service despite turbulence because of the weather. Both flights arrived before their scheduled times.
Great experience…left a bit behind schedule but made up fir that in the air and landed 10 minutes early 😁
Electric plugs didn't work. Entertainment system wasn't working
The design of the light switch on the arm rest is ridiculous.
It was ok. It was expensive to check 2 bags ($75.00 per bag), and then it took a long time to wait for shuttle to take us from one terminal to the terminal where the plane was taking off at LAX. And all of this for a flight where we had to pay for any food or drink that was not water.
It didn’t happen. I booked it and then was told it wasn’t available and then forced to pay far higher prices for a worse option
A 630departure flight Delayed 6hours! They changed my gate, I moved to the new gate. Had our flight on the screen for 12noon departure. I go get above to eat, check screen again and the flight was gone, no notice no announcement, nothing!! They sent my bag on the flight I wasn’t on, got it back to me 3days later. Thank goodness they did refund my money but I will NEVER fly them again.
Due to weather, my flight was delayed, further delayed, then canceled. I eventually got through to a support person who helped me find a different route out of MSP, but to get to DIA, they didn't want to, but eventually did help with the connection ticket purchase. But even this replacement flight was delayed time and time again, and I would have missed my connecting flights and I didn't want to get stuck in a layover city, so after 12 hours at the airport with two young boys who were very tired, we just cancelled our plans and spent the week at home, instead of Nana's.
Plane and crew on board were fine. Everything else was terrible.
The third party booking with cheapflightsfares was awful. Kayak should NOT partner with them. They sold me a bundle including seat selection and carry-on, but did not book the carry-ons with Frontier, so I’m out of pocket for $414 more while I await resolution.
This company socks. It's fraud. They canceled our flight yesterday, and today we were late because of a really long line at the check in bag. At the rebook station, there was ton of people. The workers were all rude. I am gonna make a report to FTC.
Not clean and was told I would get a great seat and it was not great at all
Horrible. I would never fly Frontier again. The booking process is tricky at best, but fraudulent in my opinion. Frontier customer service did nothing to rectify my purchase -- I ended up paying more than double what I could have gotten from other airlines and nearly triple what I thought I was buying from Frontier. Their booking practices are unfair to the consumer.
Delayed. Text notifications were slow. Not much information o what was happening. Boarding was slow and confusing. Wasn’t even offered water other flight. Had to ask. No entertainment at all. Felt like.a Greyhound bus.