MILAN (AP) — Travelers suffered hours of delays at two Milan airports after unions staged a wildcat strike during peak travel season.

Union leaders said they called the action Tuesday to protest airport plans to outsource some services to cooperatives. The strikes delayed over 60 flights at Milan's Linate and Malpensa airports, with service returning to normal by early afternoon.

The head of Italy's civil air authority, Vito Riggio, said the strikes were "unacceptable, unforgivable and unrepeatable," and called for sanctions against the strikers. He said it was "unthinkable to create difficulties for people on vacation in a touristic country."

Consumer groups said unions should pay damages for inconveniences suffered after mounting illegal strikes in a protected period. As a result of the labor action, some flights departed before baggage could be loaded.