Frontier's Economy Bundle includes a carry-on and seat choice, ideal for budget travelers.
Opt for Premium Bundle for priority boarding and extra legroom, just $20 more than Economy.

Planning a trip from Seattle to Denver? 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.
The most affordable time to fly from Seattle to Denver is typically on a Tuesday or Wednesday, with January being the cheapest month overall.
Booking Advance: Purchase tickets at least 15 days in advance for the best rates.
Cheapest Airline: Frontier Airlines generally offers the lowest fares on this route.
Direct Flights: Direct flights, particularly with Frontier, are usually cheaper than those with layovers.
Route Selection: The route from Seattle/Tacoma Intl to Denver Intl is the most cost-effective option.
AI-powered; AI can make mistakes.
| Low season | January |
|---|---|
| High season | December |
| Cheapest flight | $38 |
Direct departures
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, 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
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
1. Denial of Basic Needs (SEA): Upon arrival in Seattle, the wheelchair attendant refused my urgent request to use the restroom, insisting on scanning documents first. She eventually took me to a restroom but then abandoned me and my autistic son at an unstaffed, deserted gate for over four hours. When I called the accommodation line for help, I was told to "get someone's attention," which was impossible. My son, traumatized by the prospect of me yelling for help, was forced to wander the terminal to find assistance. 2. Revocation of Accommodations & Threats: At the gate, an agent stated I had no accommodations on file, despite my previous leg having them. When I showed the app (where my bulkhead seat was erased and replaced with Row 14), he denied the evidence. When I attempted to advocate for my immobilized leg, he threatened to "yank me from the flight" if I said one more word. He coerced me into agreeing that I was "asking for accommodations for the first time" before he would allow assistance, effectively forcing me to falsify the situation under duress. I complied only out of fear of being stranded in a strange city. 3. On-Board Negligence and Injury: Because my bulkhead seat was revoked, I was forced into Row 14. With my leg immobilized and unable to bend, it extended into the aisle. During boarding and the flight: 16 different passengers tripped over my injured leg. 6 rolled luggage bags were pulled over my injured leg. The Flight Attendant (FA) was one of the people who tripped and drove luggage over me. I reported the issue to the FA after 10 trips and 3 luggage impacts. He ignored me. He only addressed me later to ask me to move my immobilized leg for beverage service. I informed him again: "16 people have tripped, 6 luggage runovers, I cannot bend it." He provided no medical aid and no incident report. 4. Resolution and Trauma: Eventually, a different employee noticed my distress and my original paper boarding pass showing the correct bulkhead assignment. He asked me to move up. I broke down in tears, terrified that moving would cause the gate agent to remove me from the plane as threatened. We were eventually moved to the bulkhead, but the damage was done. My autistic son was traumatized by watching his mother be trampled and threatened. 5. Post-Flight: I called to report these injuries, but was disconnected after a 45-minute hold. I require a formal record of this injury and these violations.
1. Denial of Basic Needs (SEA): Upon arrival in Seattle, the wheelchair attendant refused my urgent request to use the restroom, insisting on scanning documents first. She eventually took me to a restroom but then abandoned me and my autistic son at an unstaffed, deserted gate for over four hours. When I called the accommodation line for help, I was told to "get someone's attention," which was impossible. My son, traumatized by the prospect of me yelling for help, was forced to wander the terminal to find assistance. 2. Revocation of Accommodations & Threats: At the gate, an agent stated I had no accommodations on file, despite my previous leg having them. When I showed the app (where my bulkhead seat was erased and replaced with Row 14), he denied the evidence. When I attempted to advocate for my immobilized leg, he threatened to "yank me from the flight" if I said one more word. He coerced me into agreeing that I was "asking for accommodations for the first time" before he would allow assistance, effectively forcing me to falsify the situation under duress. I complied only out of fear of being stranded in a strange city. 3. On-Board Negligence and Injury: Because my bulkhead seat was revoked, I was forced into Row 14. With my leg immobilized and unable to bend, it extended into the aisle. During boarding and the flight: 16 different passengers tripped over my injured leg. 6 rolled luggage bags were pulled over my injured leg. The Flight Attendant (FA) was one of the people who tripped and drove luggage over me. I reported the issue to the FA after 10 trips and 3 luggage impacts. He ignored me. He only addressed me later to ask me to move my immobilized leg for beverage service. I informed him again: "16 people have tripped, 6 luggage runovers, I cannot bend it." He provided no medical aid and no incident report. 4. Resolution and Trauma: Eventually, a different employee noticed my distress and my original paper boarding pass showing the correct bulkhead assignment. He asked me to move up. I broke down in tears, terrified that moving would cause the gate agent to remove me from the plane as threatened. We were eventually moved to the bulkhead, but the damage was done. My autistic son was traumatized by watching his mother be trampled and threatened. 5. Post-Flight: I called to report these injuries, but was disconnected after a 45-minute hold. I require a formal record of this injury and these violations.
Larger seats with a bit more room would be good! Thanks for all your hard work. I think we are all feeling a bit down these days economically and your positive attitudes, both from SJC to Seattle and from Seattle to Bozeman makes more of a difference than you can see! Thank you and Merry Christmas! I hope all your financial needs are met and that very good things come your way.
We flew economy, it was what I expected. The seats are too upright for me
I purchased a 1st class ticket and unfortunately the main flight attendant was not the best and seemed more interested in her phone than the passengers at times. Then the plane didn’t get restocked and the only snacks for this flight were pretzels. However I would like to say that the rest of the flight crew and ground crew at the airport we’re great, especially the people that wheeled me around the airport some and then the one getting me to the plane and the automated wheelchair that wheeled me through the airport.
Typical domestic flight. No entertainment. You have to use your own devices and provided entertainment didn’t work. Pretzels and water of flight over 4 hours is unacceptable. Meals should be provided on long flights. But it’s about the money and not customer service. You should just issue the bag of pretzels at the gate and water bottle in seat and just do away with flight attendants because they do nothing on domestic flights
Very good. Easy check in, attentive flight attendant, and on time departure/landing.
Again Alaskan and Hawaiian need to consolidate check-in, allow seat reservations on both flights. I wound up in last row because I couldn’t reserve better seat.
I would like if it had happened already. I'm still waiting for it.
Pretzels are always a disappointment. Cheezits, Sun Chips, trail mix, anything else would be nice.
Its bumpy but I can say its safe flight ,Thanks Alaska airline for bringing me in my destination😊.
Airline travel is always too cramped to really be pleasant, but the cabin crew on this flight did a pretty good job of making up for it by putting on some music during boarding and sprinkling a few funny remarks into the safety briefing and announcements, and just generally being friendly and helpful. It definitely reminded me of why I prefer the in-flight experience on Southwest!
No delays and arrived to destination 30 min early. Staff was super friendly.
San Diego airport is brand new, spacious, airy and very smooth checkin at SW baggage drop.
It was rough. The staff was unprofessional, the choice of on board drinks terrible, it was cramped in space at every airport, they always ran out of overhead bin space so they pressured people to check bags for free or we couldn’t leave on the plane— so I did check my bag to help, and they nearly lost my bag. My bag did not arrive on the luggage belt, another man on my flight and I had to waste our time going to the baggage office to search for our bags. I would only fly southwest again if it was my last choice. Also, my flights were consistently delayed over and over again— at one point they straight up told us we were waiting for the pilot to arrive.
Crew could have been friendlier, maybe I'm spoiled by SW crews. In flight wifi was good. Would be nice to have more food offerings on a 4 plus hour flight
Had to get off plane from prior flight even though I had to reboard same plane to continue to my final destination.
Everything a cheap airline should be at normal airline rates.
Plane crashed into a bus or some other vehicle on the ground while pulling out of the gate. No injuries, but wing tip was damaged and returned to gate for “maintenance issues” and we departed 5 hours later because the plane went out of service and new plane was flown in from a nearby airport, Midway.
Ever since Southwest starting charging for bags, passengers don't want to pay to check their bags, so the gate agents have to beg people to check their roller bags now because there's "not enough space". This was a terrible business move by Southwest.
Full cans of soda would be nice. A choice between two snacks would be appreciated.
Left on time, a bit delayed due to headwinds most of the trip.
I fly Delta all the time, have Platinum Medallion status. But this route seems to have major problems with delays and seems to never leave on time! Have only taken it twice in the last two weeks, and each time it had delays of more than 1 hour... very disappointed!!!!
Good seats in Main cabin, excellent service and excellent landing
My flight was cancelled with no explanation after I had already cleared security. I was given 4 options to rebook, only one being non-stop like I had paid for. I grabbed it. It was 4 plus hours later and then took off even later. Biggest complaint is that I booked early and had an aisle seat. They gave me a "window" seat in front of the exit row, so the seat did not decline. I weigh all of 103 #s and it was tight for me! For what I paid, I feel I was kind of ripped off. I think they should have given me the empty comfort seat for the inconvenience. There was no apology nor any explanation as to why the flight was cancelled. My guess is it benefitted Delta in some way.
Very smooth, on-time, and pleasantly uneventful flight. The team at the gate and on board were professional and genuinely courteous. The pilot kept us well updated throughout, and both takeoff and landing were steady and enjoyable without any drama. Just a good, solid flight. Thank you! 💗
Staff was exceptional! Everyone was kind, professional and friendly making the trip very pleasant. Thank you!
No lunch on a x-country flight scheduled for 10:50 am departure, arrived 5+ hrs later. That requires a black box label before you pay for the tickets. Worst, when I checked in online, it's specifically said that lunch was served on his flight for economy Plus passengers.
We had a lot of really rough weather but that was not Delta's fault. Pilot was amazing.
First, Delta needs more flights to/from Miami. Second, a 1000pm leaving at 1230pm is unacceptable from their biggest airport world hub. Another aircraft could have been used such as the aircraft scheduled to be used in the morning for that exact same route. Yes, I did get me there but the lack of sleep the next day didn't help me enjoy my entire trip since I was busy with activities during the weekend. This can be and is expected from Spirit (going bankrupt) and Frontier (despite they're nickel and dimers). But from Delta's World Hub? That's totally unacceptable!
This flight was straightforward and without difficulty. Service was OK, but I continue to be underwhelmed by level of attention given to Sky Priority passengers.
The entertainment available didn’t work for anyone on the flight. Long 6 hr flight with no entertainment option and the staff didn’t know until an hour into the flight when we made sure they knew about it. They had no way to fix it.
Late FA meant slow boarding. WiFi did not work. I’m a medium plus sized passenger. The seatbelt was for the first time ever barely fitting. And we delayed on the tarmac 40 min
My husband and I had boarded the flight from Denver to Chicago, and one of the last passengers to get on the plane opened the overhead bin above my husband's seat and threw his bag out of the bin to make space for his own. He said, "Mine is bigger!" The flight attendant supported the new passenger. They didn't care that my husband has two artificial knees and must have the foot room in front of his seat to be able to fit his legs in -- and to be able to stand, much less walk, at the end of the flight. I have never seen this happen before, and it was a disaster.
I understand stuff happens, but plane failures are likely due to lack of maintenance. Additionally, air conditioning wasn't working, no snack/drink service, no WiFi. Fortunately, the crew was communicative and light-hearted. United grabbed another plane and we were able to get to our destination.
Had to cancel first flight because Airporter Bus took over 3 hrs to get to airport which resulted in an extra $378 dollar fare . Is there anyway I can be reimbursed for initial fare since it was not my fault? Sent from my iPhone EJ Ledet
Excellent flight. Boarding was efficient and departure was on time. Smooth flight with on time arrival. Deplaning was also efficient.
Our flight was understandably diverted to a small regional airport in Laramie, Wyoming due to weather conditions, which I fully recognize and appreciate. However, the low rating stems from the experience that followed: passengers remained on board for over an hour without the option to deplane and stretch, despite the aircraft being stationary. Although the pilot opened the cabin door, only he was permitted to exit. Meanwhile, passengers grew increasingly uncomfortable as warm summer air entered the cabin through the open door, and being in the second row meant we were impacted immediately. While the flight attendants made efforts to keep everyone at ease, I believe allowing passengers to deplane briefly, given the extended delay, would have significantly improved the overall experience.
I never flew. Flight was canceled. DIA worst airport in the country. Avoid at all costs.
Very rough getting into denver. my kid threw up it was so rough.
Why wasn't this flight departure scheduled eith another crew so that it could leave on time? When we arrived in Denver we had so little time between flights we had run to the connecting flight. We should received some credit for the inconvenience.
I knew going into this that Frontier, being a low cost carrier, would be pretty bare bones and charge for most extras but this was made up for by the fact that the airplane was a reasonably new Airbus, every employee was great and best of all, Everett Washington is an amazing airport - thanks Frontier for flying there!!!
Seats were new and comfortable. Staff was fine. Missed my connection due to weather -which wasn’t their fault- but got no help at all. Gate staff sent me to customer service, which was and stayed unstaffed. Sign with QR code directed me to call or chat. Chat was useless. Call was returned after an hour. No itinerary offered by Frontier could get me home in less than 30 hours. Rebooked with another airline and got a partial refund that came to about 10 percent of what I paid to get home.
The experience was good. No frills but I got there safe and sound and on time.
As every law enforcement agency I could imagine surrounded the plane and we didn’t disembark for 2 hours and then had to stick around for another hour to go get our personal belongings after leaving them behind and being bused away from the plane, it was scary and inconvenient. We were given no information as to why this was happening. Lack of communication with passengers was disappointing.
Frontier Airlines was AWFUL. I was an hour early for my flight and the lady refused to check me in. I had to purchase a whole new ticket with a different airline.
Late, terrible communication, horrible planning of passenger seating until the literal last minute. One of the worst flying experiences of my life. Y'all suck
First of all, we never got on the connecting flight to Denver. They delayed our flight for two hours. If we would have gotten on that flight, we would have been stuck in Denver for 13 hours. So we re- routed our flight for a straight through flight to Oklahoma two days later. THEN, they delayed that flight for two hours. After that we were able to finally get on our flight and come home. Frontier Airlines - one of the worst airlines I have ever been on.
Terrible communication with weather delay, lost baggage, near impossible to reach customer service
My tickets got canceled on me by your site and I didn't have a flight. Then you kept sending me emails on the status of q flight I didn't have tickets for.
Flight was late. Missed connecting in Denver. My new flight is more than 24 hours later and I have no room, vouchers, or compensation, and might also be bumped from the one tomorrow.