A transatlantic flight from Paris to Detroit was diverted to Aldergrove because a passenger went into labour, it is understood.
Belfast International Airport was alerted to the emergency on Thursday afternoon and prepared for the huge Air France A340 to land.
The flight touched down at about 4.15pm and the pregnant woman was taken to hospital.
And as well as the prospect of a new arrival, the plane itself caused something of a stir as it is much bigger than those routinely flying in and out of the International.
However, the airport is among the first choices for long-haul flights that need to divert, due to the size of its runway and its ability to accommodate even large aircraft.
Its services have actually been called upon twice in less than two weeks, with a medical emergency causing a flight from Germany to Florida to be rerouted to Belfast.