A passenger jet was forced to return to Gatwick Airport part-way through its flight to Egypt after a part plunged to the ground.
Thomas Cook Flight TCX1638 left the West Sussex airport at 9am with 237 passengers on board but had to turn back a short time into its flight to Hurghada.
The object is believed to have fallen from the plane near the Kent and East Sussex border, but it was not until the jet was over Belgium that the fault was reported.
None of the passengers were injured after the over wing slide unit plummeted, which led to a probe by the Air Accidents Investigation Branch (AAIB) being launched.
A Thomas Cook Boeing 757 aircraft similar to the plane that was forced to return after a part fell off
A Thomas Cook Airlines statement said: "We can confirm that flight TCX1638, from Gatwick to Hurghada, returned to the airport after a short time into the flight after a fault was reported with an over wing slide.
"Whilst airborne, the slide unit has fallen from the aircraft and we are aware that local police have been informed.
"The aircraft landed safely at Gatwick Airport and we are now immediately undertaking a full investigation and working with the airline authorities.
"We'd like to apologise to our customers for the delay to their flight."
Thomas Cook Airlines said they have no further information from police about the slide. Passengers are due to depart on a replacement flight this afternoon.
A Kent Police spokesman said: "Kent Police was called at 11.15am to reports of an object falling from an airplane above the Langton Green and Groombridge area.
"Officers are trying to locate the object which is believed to have landed close to the Kent and Sussex border. Anyone with information should contact 101."
A Gatwick Airport spokesman said: "We can confirm that Thomas Cook flight TCX1638 returned to London Gatwick earlier this morning due to an issue with the aircraft.
"Passengers have now disembarked and are being helped by staff while the issue is investigated."
The AAIB confirmed: "The AAIB has deployed a team to London Gatwick Airport to investigate an incident to an airliner."
Sussex Police said they were also alerted at 11.15am to reports that an object had fallen from a plane.
A police spokesman said: "Officers liaised with Kent Police and searched for more than two hours around the border of the two counties but could find no trace of any item that could have come off the plane."