TMZ reported the actress complained she was sick on the flight, but felt better by the time the plane landed as scheduled.
Medics reportedly were waiting for Ryder when the flight was over and she was taken to a London hospital as a precaution.
Ryder's publicist told People magazine the actress spent about an hour at the hospital, then was "released in good health."
Ryder is best known for her roles in "Lucas," "Beetlejuice," "Heathers," "Little Women," "Edward Scissorhands," "Bram Stoker's Dracula," "The Age of Innocence," "Reality Bites," "Girl, Interrupted" and "Mr. Deeds."