On March 30, northern carriers will switch to summer schedules based on IATA slot seasons. Over 40 scheduled passenger airlines will operate between the US and Europe. While there is not much in it, examining every planned service using Cirium Diio data shows United Airlines has again replaced Delta Air Lines as the largest carrier.
US flights on the variant have risen by a fifth in a year. How the pair compare to Europe The following figure shows the two carriers' European two-way seats for sale every summer between 2014 and 2025. It is based on their schedule submissions to Cirium Diio.
Both airlines plan the highest capacity volumes to date. Delta has scheduled 9.68 million round trip seats, up over 5% from its prior high last summer.
In contrast, United has grown by almost 6% year-on-year, with 9.72 million seats available. United is less than 0.
4% larger than Delta in this sense. Nonetheless, it has regained the US-Europe throne, a position last held in 2023. United will provide about one in seven seats in this ever-important transatlantic market when all airlines are considered.
If flights were considered instead, the gap would be significantly wider. Then, United would have a tenth more services than Delta, with 40,956 round trip flights (up to 211 daily) against 37,232 (up to 194 daily). The difference is influenced by United's Boeing 757-200ERs and high-premium 167-seat Boeing 767-300ERs.
They contribute to that carrier's average seats per flight being just 237 again.
