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 | July |
| Cheapest flight | $41 |
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, 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
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
The seats were comfortable, and the boarding process was pretty smooth.
The seats were comfortable, and the boarding process was pretty smooth.
3 hour delay. Had to change plans and was still delayed.
The staff was very friendly, professional, and courteous. The overall flight was a great experience.
The crew canceled the complementary snack and drink in anticipation of turbulence that never materialized. I was counting on the drink (water) to take the the doses of medication - prescribed for my heart condition - that were due during the flight. Since no snack or meal was served on this flight, I cannot rate the food quality. Otherwise, this flight was excellent.
Departure was delayed more than 1/2 hour while we waited for luggage (only) transfer from another flight/plane. Once approved for takeoff, the flight was excellent.
We got exit row seats both flights. Everything was running on time
The flight crew was extremely rude and especially not helpful when our flight was delayed.
Pretty seamless, just a tad bit late in taking off and landing.
Flight was fine other than there was a gate change that I was not notified of. By chance I happened to check my phone and saw the change, otherwise, we would have missed our connecting flight.
Haven’t flown on SW in years. Flight was on time departing and arriving. Served vegan butter onion flavored pretzels which were bad. Coke served was in a tiny paper cup. Crew was not engaging. Felt like they were going through the motions. Old plane, tight seats and no leg room.
How can I review what was denied to me. Instead of offering to let me pay for the ticket I got booted of my flight with no way home and no choice but to purchase another ticket for 12 hours later. Filing a complaint with the DOT
From Las Vegas to Boise all went well. However, our flight was delayed in Boise and I missed my connecting flight from Seattle to Pasco. Moreover, the last flight to Pasco was full and I was booked on the 11:30 flight Sunday and given a hotel accommodation. However, I was scheduled to deliver the Sunday morning service at my church and needed to arrive no later than 10:00. Therefore, I booked a Delta flight scheduled to arrive in Pasco at 23:09. My piece of luggage checked in Las Vegas arrived in Pasco earlier today. I waited at the airport for over an hour last night to speak with an Alaska agent to no avail. I went back after church this morning in search of my piece of luggage and it could not be located. After waiting for 40 minutes to speak to the agent authorized to take my claim, he announced that he was closing the counter to assist on the flight line but not before providing me with a telephone number that would help me with filing my claim. Before I was able to make the call (due to other factors) I received a call from Alaska agent informing me that my luggage had just arrived and I am now waiting for it to be delivered. I deliberately took the more complicated route home to ensure that I would be home in plenty of time to prepare for myself for the Sunday service and accommodate my relatives’ needs. I believe the airport is undermanned given the number of flights coming in and going out. It was fiasco last night with three flights waiting for luggage and another flight landing within minutes. Today’s problems stemmed from a lack of cross training and a serious amount of cargo/baggage going out and too few people scheduled to cover.
The cabin crew was absolutely wonderful, the service was great and it was just a good flight overall.
I like them since I live in Alaska and I don't have much choice
The flight attendants were nice, but the cabin and seats were uncomfortable.
Food was terrible, noisy plane & would never pay to fly first class again. Seats in regular price are too small, no leg room & center aisle much too, too small. Seats in 1st class larger but not comfortable.
Overall, once we took off, our flight was good. Flight departure was significantly delayed due to mechanical issues. Upon arrival, it took wayyy too long to retrieve checked bags.
The ticket I purchased through Kayak did not show up in my Alaska Airlines app, and neither of the codes given to me worked for online check in. I've never had to show up to the airport at 6am wondering if I've been scammed. Cheap flight fare or whatever does not play well with airlines and I will be wary of using Kayak in the future.
Crew was rude and passive aggressive when i told them I didnt want to check my duffel bag. Then a crew member slammed my bag to the side when organizing the overhead compartment. The plane had worn leather seats with no infotainment. Plane landing was noticeably rough (this is the one year ive flown multiple times and out of american and delta this was the worst). The only redeeming quality is that we were noticeably earlier than we should have been.
The plane was delayed which was annoying. No seat back screens is a bummer. Staff if great
No in flight service, no explanation - FC got service, C+ did not, unsure about Economy. No turbulence to speak of, so I guess another way to cut cost, or promote health and well being of Delta employees? Also, boarding in MEM combined zones, and with overhead space already full on both flights after Zone 2/ Diamond, presents a huge challenge to find a space for a bag. Delta, other than point A to B, is no longer reasonable to fly - very poor experiences, not even taking into account the chastising at the gate and rude crews, across the board.
It would have been better if the flight wasn't delayed by 2.5 hours
Delta’s staff is unmatched. From the gate agents, to the pilots, to the flight attendants… all top of the industry.
Delta flight Delay for ,more that two hours i.e original flight was 6.30 PM and it starts at 8.45 PM, When we connect Delta team for meal vouchers as it is late arrival in designation,But we did not get it as per delta policy , which is not good for mid night arrival,
Inexperienced boarding crew allowed too many bags on to a full flight and delayed takeoff causing a missed connection and unplanned overnight stay. There was a hotel at the airport but Delta would not pay for it offering only to shuttle me to an area hotel. Never even offerred so much as an apology by anyone working for Delta.
Staff was great! Kind and cordial! Middle seat row 28 seat B has a hump in it. Trays were getting stuck when putting down and up. Good flight
Departure was delayed resulting in me missing my connection. Delta did not autimatically find me another flight.
The seats weren’t reclining even though it wasn’t as exit seat
It was good because we traveled without luggage, carry on only.
I usually get upgraded so my experience is usually amazing. I did not get upgraded this time - which was fine - but the wifi had issues, the monitors were going in & out, & (though not Delta's fault) one of the gentlemen next to me desperately needed a shower.
The flight was delayed by two de-icings. The seatbelt did not work correctly. It did not stay tight.
Hotter than Hades in August. Why, why do crews think that in the winter when we are already dressed for cold weather we need a cabin that is 82 degrees. Even the vents were blowing hot air.
Flight was delayed. De-icing took a while. When we landed had to wait for another plane to vacate our gate. Just an overall bad experience.
Not good - outbound flight was delayed and missed my connection even though I got to the gate after running through the airport - the agent would not let me on because the door was closed (flight had not left). There was no notification from United - overall experience was very disappointing. Additionally, I was downgraded from first class to coach on the alternative flight
United have really come back. Airport and boarding process is clear and good, app and information also very good
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
It was costly and difficult to check in. $85 to take a small suitcase with me, carry on or checked and $75 on the return trip, Plus $25 if I didn't check my self in check in $25, because I couldn't do it on the kiosk. Small very uncomfortable seats, waited on the runway for near an hour each way. It was my worst flight to date.
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.
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