One of EasyJet's Airbus A320s sustained cowling damage to one of its engines shortly after take-off from Milan Malpensa, forcing a return to the airport.
The aircraft had been operating flight 2715 to Lisbon on 12 August when, according to the carrier, it suffered a "technical issue" with one of its CFM International CFM56 engines.
EasyJet says the aircraft landed safely "using both engines". None of the 174 passengers and six crew was injured.
Italian investigation authority ANSV says part of the left-hand engine cowl detached on take-off from Malpensa's runway 35R as the aircraft departed at 18:16.
ANSV says the incident also resulted in damage to the rear fuselage and rudder of the aircraft. The twinjet flew a circuit and returned to land on the parallel runway 35L.
It has opened an inquiry into the incident, identifying the aircraft involved as a four-year old jet registered G-EZTC.
Images purporting to show the aircraft involved show cowl damage to the left-hand engine, visually similar to that suffered by a British Airways A319 in May. Investigation into the BA incident revealed that the cowls had been left unlatched before departure.
ANSV has not drawn any immediate conclusions about the EasyJet event.
"All passengers disembarked and EasyJet provided an alternative aircraft so they were able to continue their journey to Lisbon later that evening," says the budget airline.
"EasyJet is investigating the technical issue and will work alongside the relevant safety authorities according to our procedures. The safety of its passengers and crew is EasyJet's highest priority. We would like to apologise to passengers for any inconvenience experienced due to the delay."