Arsenal and Chelsea are sending as many as 6,000 unsold tickets for the Europa League final back to UEFA.
The governing body is facing the possibility of large areas of empty seats at the Olympic Stadium in Baku, as fans from both London clubs opt not to make the 5000-mile round trip to Azerbaijan's capital city next week.
The Gunners expect to have around 4,000 supporters in the stadium, having sold more than 3,000 tickets and a further 500 or so anticipated from supporters clubs from across the world, including Asia and the United States.
Chelsea, meanwhile, have sold around 2,000 of their 6,000 allocation and have sent the remainder back to UEFA.
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With the deadlines for both Arsenal and Chelsea now passed, supporters can no longer buy tickets through the clubs.
Both clubs feel they have done all they can to boost the number of fans travelling to the far east of Europe, including chartering two planes each through travel partner Thomas Cook Football.
But the high costs and limited availability of flights into the country are said to be the main deterrents for fans.
Both clubs are now keen to draw a line under the issue for now and concentrate on the game ahead - but it will be taken up with UEFA again after the dust has settled from next Wednesday's showdown.
UEFA have not received any returned tickets from sponsors, however, who have an allocation of less than 2000, which is below three percent of the stadium's 68,700 capacity.