Join Date: Sep 2005
Location: HEL
Programs: AY Platinum, TK Elite, BT Executive, AA, BA, SK, DL, NT, WB + hotels
Posts: 10,260
At least it is not possible online. It might be possible if you call. But that is not certain either. An OTA should be able to do it, but that comes with a host of other problems to deal with.
My suggestion would be to book 2 separate tickets and to stay overnight in the United States both ways.