From 26th of June, 2020 overhead bins for the storage of hand baggage will no longer be allowed on Alitalia flights.
There is a little bit confusing information on Alitalia web site as at first they state:
You are allowed one item of hand baggage weighing no more than 8kg and measuring no more than 55 cm x 35 cm x 25 cm
https://www.alitalia.com/en_us/fly-alitalia/baggage/hand-baggage.html
But bellow on this page it is written:
The groundcrew will provide an “Under the seat” label for all small luggage (no larger than 36 cm x 45 cm x 20 cm) for all domestic and international Alitalia flights for all destinations, except those operated with A330 and B777 aircraft.
https://www.alitalia.com/en_us/fly-alitalia/baggage/hand-baggage.html
And these measurements are much smaller. So before the flight you must to check with Alitalia airlines what exact carry-on luggage limits are.
Passengers will only be permitted to bring on board small baggage, that can be placed under their seat such as, for example, handbags, backpacks, laptop cases not exceeding 36 cm x 45cm x 20 cm. We invite passengers to deliver their baggage to the airport at the Check-in / Drop-off counter, to be placed in the hold, free of charge;
https://www.alitalia.com/en_en/fly-alitalia/news-and-activities/news/info-flights/flying-safely.html