Nearly 40 passenger airlines operate nonstop between Europe and the US. America’s Department of Transportation (DOT) shows that they collectively had 78.4 million passengers between April 2025 and March 2026. The collective load factor was 83.3%, which says little in itself. It is just a number.
Total traffic increased by a paltry 0.5% year-over-year. Just 351,000 additional passengers traveled, which partly reflected the political situation and the higher cost of visiting the US nowadays. As the number of available seats rose by double the rate of traffic, the load factor fell. Which routes filled the fewest seats?
The Ten Europe-US Routes With The Lowest Load Factors
DOT data was used to analyze every Europe to US route with at least 4,000 round-trip passengers in the 12 months to April 2026. They are shown in the following table and on the subsequent interactive map. Obviously, some airport pairs are served by more than one carrier. Where this is the case, the load factor relates only to the stated operator.
As always, load factor (technically, seat factor) is just one performance measure, and it should not be considered in isolation. It would be very easy to conclude that the following routes are exceptionally poor, and many were, as they have ended. However, it is always about how and why it was achieved.
The broader context is often helpful in better understanding the situation, with some services only starting relatively recently. However, big questions remain about Aer Lingus’ continuing performance to Minneapolis and Denver. Will frequencies be reduced or operating periods shortened?
4,660 (Lufthansa pulled out in April 2025, so was only just included. It was replaced by its leisure airline, Discover)
66,860 (service resumed in April 2024; read more here, although that analysis involved a different time period. Delta began this route in May 2024)
Keflavik International Airport (KEF) to Detroit Metropolitan Wayne County Airport (DTW)
29,158 (the route ended in January 2026. Delta began this route in May 2023, the same month as Icelandair)
112,036 (unclear if this relates only to the fifth freedom market or passengers continuing to/from Singapore)
Helsinki Airport (HEL) to Seattle-Tacoma International Airport (SEA)
12,997 (flights began in October 2025; I was on the inaugural service)
126,379 (the poor load was despite United’s frequency being halved, with considerably fewer seats for sale)
** In the stated period, according to the US DOT
Finnair first flew to SEA in the 1980s. The long route from HEL, which covers 4,156 nautical miles (7,697 km) each way, returned in 2022, which was during the COVID-19 pandemic. In the 12 months to March 2026, only two-thirds of the available seats were filled, which meant it was the airline’s worst-performing US route in this sense.
The oneworld member carried 30,571 passengers, which was 70.8% higher year-over-year. This was achieved on the back of capacity more than doubling (+116.6%). This expansion was due to the route’s frequency increasing from three weekly services on the Airbus A350-900 to five weekly departures on the A330-300.
Despite the airline’s partnership with Alaska Airlines, capacity far outstripped traffic, which meant that the load factor fell considerably: from 84.7% to just 66.8% in very little time. To help improve performance, Cirium Diio shows that Finnair has reduced capacity for 2026. In August, for example, seats for sale have halved compared to last August. This will improve the balance and increase loads and yields.
There are some surprisingly low results, which are driven by adding considerable amounts of capacity. Find them all out here!
Icelandair arrived in Michigan on May 18, 2023, which was two days later than Delta Air Lines’ entry. It is not unusual for another airline to begin serving the same airport pair as a competitive response. They materialized just over four years after the now-defunct Icelandic low-cost carrier WOW Air ceased flying to DTW.
Icelandair flew to DTW for more than just the summer. Flights operated through September 2025 and returned in December that year to capture Christmas-related traffic. In contrast, Delta continues to only serve the market in the summer, with the highest demand and fares.
Not coincidentally, both airlines operated on precisely the same days. Last summer, they left KEF on Mondays, Tuesdays, Wednesdays, Fridays, and Sundays. This did not help Icelandair’s performance. With a load factor of just 64.1%, 20 percentage points lower than for its overall US routes, Icelandair pulled out on January 3, 2026. Delta will benefit as a result.
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