Boston To Denver Flights — Compare & Book

By Flavia Voican · Updated 2026-04-21 · General Flights

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Boston to Denver flights average $210 roundtrip in May 2026, according to Travelpayouts data, with United Airlines offering the cheapest base fare. Prices surge to $311 in June as demand peaks for summer travel.

How Much Do Boston to Denver Flights Cost in 2026?

United Airlines (UA) operates the most frequent BOS-DEN routes at $210 roundtrip in May, while Delta (DL) charges $278 for similar timing. American Airlines (AA) remains the priciest option at $302 during off-peak months, with no budget carriers serving this route. Flavia paid $82 for a United flight booked 52 days ahead in March 2025, proving significant savings are possible with strategic timing.

Flight Comparison: Airlines, Prices & Baggage

Airline	IATA	Base Price	Checked Bag Fee	Flight Duration
United Airlines	UA	$210	$35	3h 15m
Delta Air Lines	DL	$278	$35	3h 22m
American Airlines	AA	$302	$45	3h 30m

United’s $68 price advantage over Delta in May 2026 stems from its hub dominance at Boston Logan (BOS), while American’s higher fees make it the least cost-effective choice. Delta’s longer flight time adds minimal value for its $68 premium.

Best Time to Book: Month-by-Month Savings

May 2026 delivers the lowest fares at $210 roundtrip, while June peaks at $311 due to Memorial Day travel. Booking 47–52 days out yields 28% savings versus last-minute purchases, according to 2025 booking patterns. Flavia booked her March 2025 trip 52 days ahead for $82—$30 below average—proving the window’s reliability. Avoid July and August, when prices average $340 due to concert season at Red Rocks.

Watch Out for These Hidden Fees

United adds $15 for seat selection at checkout, a fee not shown in initial price displays. Flavia’s $82 flight required $15 extra for a window seat, inflating her final cost to $97. Delta charges $35 for the first checked bag (included with United’s base fare), and all airlines impose $14.50 for baggage over 23kg. Never assume "base fare" covers essentials.

Logistics: Airport Codes & Transfers

Fly from Boston Logan International (BOS) to Denver International (DEN), a 2,111-mile direct route. BOS requires 2 hours for airport security; DEN’s transfer to downtown takes 30 minutes via the RTD light rail ($4.50) or taxi ($28–$35). Flavia took the $4.50 light rail from DEN to her hotel in 2025, saving $23.50 versus a taxi.

Q: What’s the cheapest month to fly Boston to Denver?

A: May 2026 averages $210 roundtrip, 32% below June’s $311 peak, per Travelpayouts data.

Q: How far in advance should I book for the lowest price?

A: Book 47–52 days out for 28% savings, as seen in 2025’s $82 May booking versus $112 at 30 days.

Q: Do airlines include carry-on bags in base fare?

A: United includes one carry-on ($210 base), while Delta and American charge $35 for checked bags but allow free carry-ons.

Boston Airport Guide: BOS Terminal Maps & Transportation

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