Join Date: Aug 2008
Location: South Park, Metropolis
Programs: AA LT PLT 3MM, Marriott Ambassador, Hilton GLD, IHG PLT, Club Carlson VIP
Posts: 4,666
Did you try the search function for stopover?
Most European flights may go through London, and you can stay there as long as its under 24hrs for your connection to Helsinki. There is a seasonal ORD-HEL flight though. All AA international award travel are allowed a stopover to/from the US gateway city.