United Airlines is one of the largest full-service carrier with a vast network of domestic and international routes operating out of its major hubs at Chicago-O’Hare (ORD), Newark (EWR), Denver (DEN), Houston-Intercontinental (IAH), and Washington-Dulles (IAD) among others. United’s network has been designed to serve high-frequency business segments and long-haul international routes, aided by a base of robust domestic connections.
In 2025, United’s busiest routes are still driven by strong demand along the East and West Coasts and the central United States, particularly on high-density business routes and trunk routes between major cities. This article covers the Top 100 busiest United Airlines routes by average monthly flights, published seats, and available seat miles (ASMs).

Leading United’s Domestic Operations
Topping United’s busiest routes is the intra-regional shuttle between New York-LaGuardia (LGA) and Chicago-O’Hare (ORD), with 844 average monthly flights and over 140,000 seats a month. Following close behind are other dominant business corridors including Washington-National (DCA) to ORD and EWR to ORD, both of which are the key routes of United’s East Coast-to-Midwest network.
Notably, the transcontinental San Francisco (SFO) to Newark (EWR) route is the fourth busiest in frequency but the largest in terms of ASMs at over 402 million available seat miles per month. This reflects the initial deployment of premium widebody aircraft such as the Boeing 777 and 787 to operate a split of high-yield business and long-haul leisure traffic.
For easier readability, the complete dataset is split into two tables, and each contains 50 routes.
Top 100 Busiest United Airlines Routes
Rank | Route | Flights | Seats | ASMs |
---|---|---|---|---|
1 | New York-La Guardia (LGA) - Chicago-O'Hare (ORD) | 844 | 140104 | 102696232 |
2 | Washington-National (DCA) - Chicago-O'Hare (ORD) | 678 | 95948 | 58720176 |
3 | New York (EWR) - Chicago-O'Hare (ORD) | 652 | 115900 | 83332100 |
4 | New York (EWR) - San Francisco (SFO) | 649 | 156962 | 402607530 |
5 | Denver (DEN) - Houston-Intercontinental (IAH) | 641 | 131152 | 112921872 |
6 | Houston-Intercontinental (IAH) - Chicago-O'Hare (ORD) | 637 | 123700 | 114422500 |
7 | Chicago-O'Hare (ORD) - San Francisco (SFO) | 637 | 152901 | 282255246 |
8 | Denver (DEN) - Chicago-O'Hare (ORD) | 621 | 137578 | 122169264 |
9 | Los Angeles (LAX) - Chicago-O'Hare (ORD) | 615 | 125136 | 218362320 |
10 | Houston-Intercontinental (IAH) - San Francisco (SFO) | 606 | 120034 | 196255590 |
11 | Denver (DEN) - San Francisco (SFO) | 596 | 127995 | 123771165 |
12 | Los Angeles (LAX) - San Francisco (SFO) | 592 | 98575 | 33219775 |
13 | New York (EWR) - Los Angeles (LAX) | 585 | 137575 | 337609050 |
14 | New York (EWR) - Orlando (MCO) | 570 | 100093 | 93887234 |
15 | Denver (DEN) - Los Angeles (LAX) | 551 | 103712 | 89399744 |
16 | Houston-Intercontinental (IAH) - Los Angeles (LAX) | 548 | 101779 | 140353241 |
17 | Houston-Intercontinental (IAH) - New Orleans (MSY) | 490 | 72218 | 22026490 |
18 | Denver (DEN) - New York (EWR) | 470 | 83570 | 134129850 |
19 | New York (EWR) - Houston-Intercontinental (IAH) | 469 | 82869 | 116016600 |
20 | Boston (BOS) - Chicago-O'Hare (ORD) | 468 | 81380 | 70556460 |
21 | Houston-Intercontinental (IAH) - Las Vegas (LAS) | 459 | 80381 | 98225582 |
22 | Houston-Intercontinental (IAH) - New York-La Guardia (LGA) | 456 | 74720 | 105803520 |
23 | Denver (DEN) - Washington-Dulles (IAD) | 454 | 101993 | 148093836 |
24 | Las Vegas (LAS) - San Francisco (SFO) | 451 | 77635 | 32140890 |
25 | Austin (AUS) - Houston-Intercontinental (IAH) | 449 | 64591 | 9042740 |
26 | San Diego (SAN) - San Francisco (SFO) | 446 | 76155 | 34041285 |
27 | Washington-Dulles (IAD) - Los Angeles (LAX) | 445 | 89159 | 203995792 |
28 | Denver (DEN) - Las Vegas (LAS) | 437 | 77922 | 49012938 |
29 | Washington-Dulles (IAD) - San Francisco (SFO) | 434 | 93031 | 225041989 |
30 | New York (EWR) - London-Heathrow (LHR) | 434 | 72478 | 251208748 |
31 | Houston-Intercontinental (IAH) - Orlando (MCO) | 423 | 76818 | 65525754 |
32 | Minneapolis/Saint Paul (MSP) - Chicago-O'Hare (ORD) | 418 | 64738 | 21622492 |
33 | Washington-National (DCA) - Houston-Intercontinental (IAH) | 411 | 57178 | 69071024 |
34 | New York (EWR) - West Palm Beach (PBI) | 395 | 68960 | 70615040 |
35 | Houston-Intercontinental (IAH) - San Antonio (SAT) | 383 | 58841 | 11238631 |
36 | Las Vegas (LAS) - Chicago-O'Hare (ORD) | 383 | 71348 | 108092220 |
37 | Dallas/Fort Worth (DFW) - Houston-Intercontinental (IAH) | 381 | 51266 | 11483584 |
38 | New York (EWR) - Las Vegas (LAS) | 378 | 66205 | 147438535 |
39 | Denver (DEN) - Phoenix (PHX) | 376 | 66504 | 40035408 |
40 | Chicago-O'Hare (ORD) - Phoenix (PHX) | 376 | 69118 | 99529920 |
41 | Washington-Dulles (IAD) - Houston-Intercontinental (IAH) | 372 | 62212 | 74032280 |
42 | Washington-Dulles (IAD) - Chicago-O'Hare (ORD) | 372 | 64871 | 38209019 |
43 | Washington-Dulles (IAD) - Orlando (MCO) | 371 | 68147 | 51655426 |
44 | Orlando (MCO) - Chicago-O'Hare (ORD) | 367 | 73461 | 73828305 |
45 | Cleveland (CLE) - Chicago-O'Hare (ORD) | 363 | 55547 | 17552852 |
46 | Denver (DEN) - San Diego (SAN) | 360 | 64044 | 54629532 |
47 | Boston (BOS) - Denver (DEN) | 358 | 66139 | 116007806 |
48 | Dallas/Fort Worth (DFW) - Chicago-O'Hare (ORD) | 356 | 51597 | 41380794 |
49 | New York (EWR) - Fort Lauderdale (FLL) | 355 | 62739 | 66817035 |
50 | Austin (AUS) - Denver (DEN) | 354 | 53173 | 41209075 |

The Other Half: United Airlines Busiest Routes
Rank | Route | Flights | Seats | ASMs |
---|---|---|---|---|
1 | New York-La Guardia (LGA) - Chicago-O'Hare (ORD) | 844 | 140104 | 102696232 |
2 | Washington-National (DCA) - Chicago-O'Hare (ORD) | 678 | 95948 | 58720176 |
3 | New York (EWR) - Chicago-O'Hare (ORD) | 652 | 115900 | 83332100 |
4 | New York (EWR) - San Francisco (SFO) | 649 | 156962 | 402607530 |
5 | Denver (DEN) - Houston-Intercontinental (IAH) | 641 | 131152 | 112921872 |
6 | Houston-Intercontinental (IAH) - Chicago-O'Hare (ORD) | 637 | 123700 | 114422500 |
7 | Chicago-O'Hare (ORD) - San Francisco (SFO) | 637 | 152901 | 282255246 |
8 | Denver (DEN) - Chicago-O'Hare (ORD) | 621 | 137578 | 122169264 |
9 | Los Angeles (LAX) - Chicago-O'Hare (ORD) | 615 | 125136 | 218362320 |
10 | Houston-Intercontinental (IAH) - San Francisco (SFO) | 606 | 120034 | 196255590 |
11 | Denver (DEN) - San Francisco (SFO) | 596 | 127995 | 123771165 |
12 | Los Angeles (LAX) - San Francisco (SFO) | 592 | 98575 | 33219775 |
13 | New York (EWR) - Los Angeles (LAX) | 585 | 137575 | 337609050 |
14 | New York (EWR) - Orlando (MCO) | 570 | 100093 | 93887234 |
15 | Denver (DEN) - Los Angeles (LAX) | 551 | 103712 | 89399744 |
16 | Houston-Intercontinental (IAH) - Los Angeles (LAX) | 548 | 101779 | 140353241 |
17 | Houston-Intercontinental (IAH) - New Orleans (MSY) | 490 | 72218 | 22026490 |
18 | Denver (DEN) - New York (EWR) | 470 | 83570 | 134129850 |
19 | New York (EWR) - Houston-Intercontinental (IAH) | 469 | 82869 | 116016600 |
20 | Boston (BOS) - Chicago-O'Hare (ORD) | 468 | 81380 | 70556460 |
21 | Houston-Intercontinental (IAH) - Las Vegas (LAS) | 459 | 80381 | 98225582 |
22 | Houston-Intercontinental (IAH) - New York-La Guardia (LGA) | 456 | 74720 | 105803520 |
23 | Denver (DEN) - Washington-Dulles (IAD) | 454 | 101993 | 148093836 |
24 | Las Vegas (LAS) - San Francisco (SFO) | 451 | 77635 | 32140890 |
25 | Austin (AUS) - Houston-Intercontinental (IAH) | 449 | 64591 | 9042740 |
26 | San Diego (SAN) - San Francisco (SFO) | 446 | 76155 | 34041285 |
27 | Washington-Dulles (IAD) - Los Angeles (LAX) | 445 | 89159 | 203995792 |
28 | Denver (DEN) - Las Vegas (LAS) | 437 | 77922 | 49012938 |
29 | Washington-Dulles (IAD) - San Francisco (SFO) | 434 | 93031 | 225041989 |
30 | New York (EWR) - London-Heathrow (LHR) | 434 | 72478 | 251208748 |
31 | Houston-Intercontinental (IAH) - Orlando (MCO) | 423 | 76818 | 65525754 |
32 | Minneapolis/Saint Paul (MSP) - Chicago-O'Hare (ORD) | 418 | 64738 | 21622492 |
33 | Washington-National (DCA) - Houston-Intercontinental (IAH) | 411 | 57178 | 69071024 |
34 | New York (EWR) - West Palm Beach (PBI) | 395 | 68960 | 70615040 |
35 | Houston-Intercontinental (IAH) - San Antonio (SAT) | 383 | 58841 | 11238631 |
36 | Las Vegas (LAS) - Chicago-O'Hare (ORD) | 383 | 71348 | 108092220 |
37 | Dallas/Fort Worth (DFW) - Houston-Intercontinental (IAH) | 381 | 51266 | 11483584 |
38 | New York (EWR) - Las Vegas (LAS) | 378 | 66205 | 147438535 |
39 | Denver (DEN) - Phoenix (PHX) | 376 | 66504 | 40035408 |
40 | Chicago-O'Hare (ORD) - Phoenix (PHX) | 376 | 69118 | 99529920 |
41 | Washington-Dulles (IAD) - Houston-Intercontinental (IAH) | 372 | 62212 | 74032280 |
42 | Washington-Dulles (IAD) - Chicago-O'Hare (ORD) | 372 | 64871 | 38209019 |
43 | Washington-Dulles (IAD) - Orlando (MCO) | 371 | 68147 | 51655426 |
44 | Orlando (MCO) - Chicago-O'Hare (ORD) | 367 | 73461 | 73828305 |
45 | Cleveland (CLE) - Chicago-O'Hare (ORD) | 363 | 55547 | 17552852 |
46 | Denver (DEN) - San Diego (SAN) | 360 | 64044 | 54629532 |
47 | Boston (BOS) - Denver (DEN) | 358 | 66139 | 116007806 |
48 | Dallas/Fort Worth (DFW) - Chicago-O'Hare (ORD) | 356 | 51597 | 41380794 |
49 | New York (EWR) - Fort Lauderdale (FLL) | 355 | 62739 | 66817035 |
50 | Austin (AUS) - Denver (DEN) | 354 | 53173 | 41209075 |
United’s Network Strength in 2025
The busiest routes highlights United’s reliance on its central hubs for network reach and scheduling flexibility. Chicago-O’Hare (ORD) remains the pillar of United operations, a hub for connections to the East Coast, West Coast, and overseas destinations. Routes such as ORD–San Francisco, ORD–Denver, and ORD–Los Angeles are consistently among the ones offering the most seats.
Denver (DEN) and Houston-Intercontinental (IAH) are equally vital to connecting United’s mountain and southern operations. The Denver–Houston and Denver–Chicago routes offer more than 120,000 monthly seats each, in line with strong cross-country demand. Furthermore, IAH as a southern gateway is especially illustrated through its connections to San Francisco, Los Angeles, and numerous Florida cities.
Coastal transcontinental operations such as EWR–LAX and EWR–SFO also stand out for their high ASMs, both in excess of 330 million a month, based on the use of widebodies with premium cabin arrangements and lie-flat seating. They are United’s corporate and premium anchor against Delta and American, particularly in New York and California markets.

Route Strategy and Hub Dynamics
United’s domestic route network in 2025 remains targeted on high-density business travel corridors and strong hub-to-hub operations. Intra-hub routes such as IAH–ORD, DEN–ORD, and DEN–IAH see some of the highest traffic, allowing good connectivity within the network. Trunk routes are timed multiple times a day on narrowbody mainline jets, allowing flexibility in connecting onward schedules.
On the East Coast, the carrier has a robust presence in Newark (EWR), with high-demand routes such as Orlando, Fort Lauderdale, and West Palm Beach — routes that combine VFR traffic with year-round vacation loads. These vacation markets typically have high load factors and seasonal frequency enhancements.
In the western United States, United Airlines maintains its San Francisco (SFO) and Los Angeles (LAX) hubs to anchor Pacific connectivity and cross-country capacity. SFO–LAX, despite a 90-minute flight, is one of the busiest short-haul routes in the United network, with nearly 600 flights per month. It also feeds the airline’s transpacific traffic by shoving passengers into western gateway cities.

Long-Haul and International Standouts
Of the top 100 routes, London Heathrow (LHR)–EWR is the busiest international route by ASMs, with 251 million available seat miles per month. Also noteworthy is United’s intra-North America network, featuring high-frequency routes to Mexico City (MEX), Cancun (CUN), and Vancouver (YVR) as the hub for cross-border traffic from Houston, San Francisco, and Denver. United’s Houston–Cancun alone carries an average of nearly 63,000 seats monthly.
As a whole, the Top 100 busiest United routes of 2025 indicate a highly concentrated network, high-yielding, and optimized for frequent hub-to-hub connections and premium cross-continent flights. While United has expanded heavily outside of the U.S., its biggest strength is still its U.S. domestic base — connecting big cities with high frequency and flexibility.
In an age of competitive equilibrium increasingly characterized by dynamic schedules and fluid passenger demand, United’s network has the size and scope to compete in every corner of the market — from regional routes to ultra-premium corridors.
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Sources: Cirium Diio