DUBLIN, Jan 7 (Reuters) - Flutter, the world's largest online betting company, said on Tuesday it expects 2024 earnings at its fast-growing U.S. FanDuel brand to be sharply lower after American football gamblers enjoyed an unprecedented winning streak.

Bookmakers generally suffer when favourites win, and Flutter said the NFL season to date has been the most customer-friendly since the lifting of a U.S. ban on sports betting in 2018, with the highest rate of NFL favourites winning in almost 20 years.

It now estimates U.S. revenue to be some $370 million lower than the midpoint of its previous guidance of about $5.78 billion and U.S. adjusted earnings to be about $205 million lower than the previous midpoint of around $505 million.

Flutter's U.S.-listed shares were 1.7% lower in extended trading.

The Irish-founded company said it fared better elsewhere in recent weeks where a run of more favourable sports results for bookmakers meant it now estimates 2024 full-year revenue and adjusted EBITDA outside the U.S. will be about 1% and 2% higher respectively than the midpoints of its prior guidance.

It previously forecast midpoint adjusted EBITDA of $1.82 billion for its non-U.S. brands, which include Paddy Power, Betfair and Sportsbet.

Flutter also said the transitory nature of the results had no impact on the longer-term guidance it provided in September that anticipated the booming U.S. market would account for almost half of an expected doubling of profit by 2027.