Italy's civil aviation authority has warned Volotea that it could be blocked from operating within the country if its flight schedules continue to be disrupted.
ENAC says its director general Alessio Quaranta has written to the Spanish budget carrier to highlight "numerous critical issues" during the summer, including flight cancellations, overbooking and "long delays" that have caused inconvenience to passengers and disruption at Italian airports.
Volotea is being urged by ENAC to take "immediate corrective action".
Failure to resolve the issues would prompt ENAC to suspend Volotea's permission to operate in Italy from 15 September.
ENAC also says that it is investigating "numerous" reports that the Barcelona-based carrier has failed to comply with EU regulation 261. The authority says that if these reports are verified it will seek to impose the "maximum penalty".
Responding to ENAC's statement, Volotea argues that, despite the "adverse" impact of ATC delays in Europe this year, it has maintained an above-average punctuality ratio and a cancellation rate "among the lowest in the industry".
It adds: "As for all airlines, it is not always possible to avoid disruptions when ATC and other external factors affect network capacity and scheduled operations. Volotea co-ordinates client assistance with subsequent flights, agreements with associated airlines, alternative transportation means and hospitality when needed.
"Volotea always does its best to ensure that passengers are properly assisted and informed at all times."
Earlier this month, ENAC disclosed that it was investigating the operations of Blue Panorama, Ryanair, Volotea and Vueling following disruption this summer.
On 19 July, ENAC revoked TACV's authorisation to operate within Italy, citing the inconveniencing of passengers flying between the country and Cape Verde with the African state's flag carrier. But the authorisation was reinstated a day later.