Melania Trump's plane has been forced to return to a Washington DC area military base because of smoke in the cabin.
A spokeswoman for the First Lady said "everyone is fine and everyone is safe" after the plane returned to Joint Base Andrews on Wednesday.
President Trump's wife later boarded a different plane to make the visit to a Philadelphia hospital.
According to TV reporters travelling with the First Lady the flight was in the air for about 10 minutes when smoke filled the cabin, and then US Secret Service agents rushed to the front of the plane.
It is not clear what caused the problem.
Once at the Philadelphia hospital, Melania toured a neonatal intensive care nursery and spoke at a conference on a new system that tracks infants suffering opiate withdrawal.
The visit was part of her Be Best campaign, which focuses on issues affecting children, including the importance of healthy pregnancies.
Australian Associated Press
