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.
This feature is powered by ChatGPT: an OpenAI-developed artificial intelligence model trained with KAYAK proprietary data and third-party data not verified by KAYAK.
| Low season | January |
|---|---|
| High season | July |
| Cheapest flight | $55 |
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, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Wednesday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
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, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
Wednesday
Alaska Airlines, Delta, Frontier, +2 more
Alaska Airlines, Delta, +3 more
1
2
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
Check in went pretty well and you didn't lose my bag. After I got a drink from the drink cart they charged me for it, and at the crazy overpriced airport rates. Never had that happen before, is that an american thing? what madness.
Check in went pretty well and you didn't lose my bag. After I got a drink from the drink cart they charged me for it, and at the crazy overpriced airport rates. Never had that happen before, is that an american thing? what madness.
In both halves of the trip (going and returning) there were problems. Not exactly Alaska's fault, but still really difficult. Outgoing flight was canceled and rebooked twice due to a total ground stop of all Alaska's flights. This required me to change airports with minimal notice and I almost missed my flight transferring to the other airport (which was roughly an hour and a half away). On the return, the first leg was delayed by an hour, and the second leg was delayed by nearly 3 hours. This was a rough set of flights and the communication about all of these changes was minimal. Crew did their best however, so no fault there. Other thing to remember is there is no food on Alaska flights unless you pre-order. Take that into account when you choose airlines.
My flight was canceled because of an IT outage, and they did not answer the phone for 8 hrs. There was no next flight out, I have missed my wedding because of this.
Liked the crew. Multiple delays. Altered my complete day and plans
Apart from the man snoring very loudly across the aisle from us for about 3.5 of the 5 hour flight it was a great flight. I couldn't get the internet to work and stay working. Texting was intermittent for me.
The plane boarded late and arrived late which wasn't really ideal.
The pretzels have no taste. How about a choice of snacks? The flight itself was fine.
This was my first time using Alaska. The best thing about Alaska is the people. Everyone that I had any contact with couldn’t have been better. So far on this trip no complaints. I will use Alaska again
Full, attentive service from the fist class cabin flight attendant was superb. Really exceeded expectations.
The stewards were too loud and chatty with each other
Staff were friendly and happy. Delta could make sure passengers that don't have the app know of changes. Without Kayak I would not have known about the change of gate or the delay. Kayak was faster to notify me.
They ended up paying for the bag twice, but the counter wouldn't take my baggage receipt. Left it to me to resolve. Not sure how to resolve the issue.
The customer service before board was very rude and when I expressed my concerns about making the connecting flight she laughed and told me I bought the wrong ticket. I explained once it showed the flight was delayed it no longer let me change seats or anything. I was trying to upgrade to make sure I would get to the next gate on time.
Non stop on long haul is the way to go. Great experience
The flight used a B767 with a very old interior from before 2014. The entertainment system did not work at all during the flight despite attempts to reset the system. It was like they flew this route just to be competitive.
They changed planes and the new plane couldn’t carry enough fuel to fly across the country so we had to stop in Kansas City to refuel. Flight was delayed .
Flight was too crowded and seats are too small, especially since passengrs are getting larger. Having a middle seat is ALWAYS tough! Woman on my left was large & kept creeping in to my space. Flight personnel were great! Have more savory rather than sweet snacks please.
Flight was crowded and the woman sitting on my left was large & kept crouching in to my space. You need bigger seats or smaller passengers to fit into the seats you DO have! Snack were OK. Would appreciate if airlines had more savory rather than sweet snacks, thank you!
Delayed flight (1hour) plus a long layover after an overnight flight with no backup plane available.
Flight delayed for two and half hours and then canceled altogether due to mechanical issues. No mechanic onsite to fix so had to send one from LAX.
Canceled my flight within 24 hours, causing me arriving home midnight. Will never book Hawaiian airlines anymore
I like Hawaiian, it was great that they had good internet connection across the Pacific Ocean, thanks to Star Link satellites. The seating was comfortable, ( I was in economy ). Maybe I missed it, but I only got offered a beverage once. It was a nonstop flight KOA to SMF. I would take it again next time I go that way.
I always love flying Hawaii and I have nothing to add
Previously flown Hawaiian Airlines on similar routes, I found Alaska Airlines to be noticeably more comfortable. The seats on Alaska Airlines provided better support and cushioning, which made a significant difference on the long flight to the islands. When you’re spending 5-6 hours in the air, seat comfort really matters, and Alaska Airlines delivered where it counts. After comparing both carriers, I’ve decided to book with Alaska Airlines for all my future Hawaii trips. The superior seat comfort alone makes it worth choosing Alaska over Hawaiian Airlines. If you’re planning a trip to Hawaii and prioritizing comfort, I’d recommend giving Alaska Airlines a try. You won’t be disappointed. Highly recommended for Hawaii travel!
I received several emails about my 3:10 flight. When I showed up to the airport at 12:30 to check my bags I was told the flight was actually at 1 pm. They grudgingly rebooked me for a flight at 5:22 to Vegas to get a connecting to LAX. I did find the gate for my original 3:10 flight but they were booked. I proceeded to receive status updates and gate change information for the 3:10 flight, even though I was apparently never supposed to be on that flight
My flight was delayed three hours and then cancelled. The gate agent proceeded to rebook me in a middle seat without telling me and I was placed between two large individuals who did not fit in their own seats and instead took up most of mine. It was an awful experience.
The food options were limited and very specific. Some type of entertainment option for a 4.5 hour flight would have been nice.
Flight was smooth and comfortable. We were able to check a bag at counter due to full flight and boarded with an earlier group. We were there very early and didn’t hear the gate change just noticed our flight was no longer displayed st the gate. There were two other flights with gate shuffles - may be unavoidable but not desirable. First time I had to print my own luggage tag and attach at arrival. Not a fan of that process.
The crew was EXTREMELY helpful And sweet and the flight was smooth!
I received an email from Kayak with confirmation number for Hawaiian and another for Alaska. I received emails from Kayak for both my outbound and return flight to say "time to check in." Despite trying each number (Hawaiian and Alaska), I could not check in for outbound or return. It was then confusing at the airport - I hda "no place to go" to figure out how to check in. All the kiosks are marked "scan bag,etc." I wandered around with no agent to talk to. That was a bit stressful. Either Kayak, or airline, needed better communication on what to expect and to do.
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.
leg space better than expected. two washrooms for one plane isn't enough.
The gate attendant let me walk right by her with a bag too big for the overhead compartment
Terrible. The canceled my entire flight when I requested a refund for a trip frontier canceled trip one way.
Frontier is the Walmart of airlines. Frontier has removed adjustability and comfort from their seats to make the flight lighter and save gas. This makes it impossible to sleep on their flights. Their customer service is abysmal. Once, I bought a drink on the plane, and they swiped my credit card on the plane to pay for it. Then I got three weeks of daily notices from my bank telling me they tried to charge the wrong card number over and over again. I tried to call them, but they removed the ability to actually talk to someone that can resolve such a problem from their company to cut corners. The only way to talk to someone in person is to go to the check-in counter at the airport (40 minutes drive from my house). Eventually their system gave up on trying to charge the card, after 21 days of repeated tries. They don't pad their prices even a little to handle customer service issues like missed flights. They also have a blanket policy preventing helping you reschedule a missed flight if their system says you "cancelled" your own flight online. This is a major problem because their website is broken on mobile devices, the only web browser you have at the airport when their gate staff tell you that you have to reschedule your own missed flight online because they can't help you. I tried to reschedule my flight on my android device and instead, their website crashed and "cancelled" my missed flight. When I got to the counter, the agent argued with me for 5 minutes insisting that I intentionally cancelled my own flight (implying I had to buy another flight). She missed the point: the problem was that I could not buy another flight because their website is broken. I left to avoid more conflict with the "customer service" agent. I tried to redress my issue with their only other "customer service" chanel available: the contact form on their website. The response I got was more of the same: you cancelled your own flight, according to our website / computer records, therefore we won't help you. I was trying to explain the problem with their broken website that cost me hundreds of dollars by crashing / malfunctioning and resulting in a cancelled flight, but they only had deaf ears for this problem. Worst customer service I have ever experienced. I will never buy another Frontier flight again, because it is a risky, painful move that I will likely regret often.
What I expected, nickeled and dined and a frontier flight attendant loudly complained about her job and lack of communication as she headed to the gate on her cell phone. Not professional.
I’m not gonna fly Frontier Airlines because booking is not an option. No water or food is for high price, not equipped for health emergency incompetent crew for emergency services. Cheap airline shows it is cheaper in all service categories. Boarding is the best of all airlines!
Very bad! No good service delayed my second connection flight
Frontier is terrible. Paid for exit row, not given exit row, refused to refund fee.
2 hour delay due to late plane, wrong size plane causing overbooking, and people getting off and on the plane after boarding was completed.
The worst. We never made our connection and they did absolutely nothing to help us at the airport.
I never got to experience the flight because they delayed my first flight and I missed this one. Then Frontier didn't want to help me rebook a flight to get me to my final destination.
The Boarding process in Denver was chaotic, and since the line was so long, we were lined up very far from the gate. If there were any announcements from the gate staff, we didn't hear them. The flight attendants were spectacular. The only negative part of the flight was sitting by a 2 1/2 year old who was unruly and unfortunately had parents that matched his behaviors. Also, the restaurants in Denver on the E concourse, they didn't have food (passengers could only order 1 item on the entire menu) or the restaurants had 12-14 people waiting for orders to be prepared and another 6 people waiting to order. If you have a layover in Denver and need to grab food, be prepared to visit the shops with pre-packaged sandwiches, or you can visit another concourse but it may take a while to transit throughout the airport.
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