We did these in the last few years of the JFK-BUD flight where we connected to One World's Malev, who now has been out of business for about 3 years. It was an easy connection both ways including other destinations in the former Eastern bloc. When we connected from IST there must have been 40-50 passengers making this connection from a full AA 763. Too bad Malev is not around any longer. Only a few passengers went on to Sofia when we did that connection.