They warn that a draft law could breach EU free market rules, but the Italian government is reluctant to stand aside and watch as flight prices soar.
The draft decree, still subject to change, forbids companies from raising fares for Sicily or Sardinia beyond a level that is “200 per cent higher” than the average price for such routes.
Both islands are popular tourist destinations but poor connections to the mainland mean locals and visitors alike are forced to pay high air fares during the peak season.
The Italian Board of Airlines Representatives and Assaereo trade associations complained in a joint statement that the government did not discuss the issue with them.
They said negotiations could have found “less punitive solutions”.
They also said the price controls “appear to be in conflict with the applicable sector regulations”, which generally allow airlines operating in the EU “to choose the routes on which to operate and to freely set passenger and cargo fares”.
Companies including Lufthansa, easyJet, American Airlines and Delta are members of the IBAR, the association's website shows.
The groups called on the government to reconsider its decision, warning that “any attempt to restrict the freedoms of the sector and the competition that characterises it” could negatively affect supply and ticket prices, as well as employment levels in the airline sector and related industries.
Ticket prices to Sicily and Sardinia have risen sharply in recent weeks.
Prime Minister Giorgia Meloni's cabinet was set to approve on Monday a decree law that covers a range of subjects including support for strategic industries, taxi licences, a blue crab invasion as well as airline prices.
Measures in a decree law take effect immediately, but parliament has to ratify them within two months, otherwise they lapse.
Parliament can also amend the contents of a decree during the ratification procedure.
Devastation brought on by wildfires in Sicily last month forced the evacuation of tourists and airport services were disrupted.
As Italy struggled with a heatwave, Ms Meloni's administration approved a decree that allowed construction and agricultural companies to furlough staff in areas with high temperatures without penalty.