Question:
How did they expect them all to get there?
Airlines flying year-round to Falcone Borsellino Airport (PMO) in Palermo, Italy: Air Italy, Air Malta, Alitalia, Danish Air Transport, easyJet, easyJet Switzerland, Eurowings, Lufthansa, Pobeda, Ryanair, Transavia France, Tunisair, Volotea, and Vueling. Add in airlines flying seasonal routes to Palermo, and you have probably another 20 airlines, including Air France and British Airways. Alitalia is in SkyTeam, and Lufthansa in Star Alliance, which means you would also be able to codeshare flights through Delta, United, and every other airline in those alliances.
So the answer would be: Any of the regularly-scheduled flights offered by the dozens of airlines that operate (either directly or though their alliance partners) flights to Palermo.