Italy's pilot union, the IPA, has raised concerns over the planned merger of carriers Alitalia, WindJet and Blue Panorama.
It said that competition will be harmed by the consolidation, announced on 25 January, with customers facing higher prices and fewer flight options.
The process is being driven by Alitalia's poor performance compared to its peers, said IPA president Giovanni Galiotto.
"For Alitalia it is vital to increase revenue per passenger and load factors which are still well below the average of the European bigger airlines. Alitalia is not strong enough in its domestic market and has finally decided to buy some of its direct competitors," he said.
Galiotto believes all three carriers are struggling financially, with investors, particularly in Alitalia's case, unwilling to pump any more money into the airline.
IPA is also worried that another round of redundancies will sweep through the sector on the back of the merger. It said 800 pilots were laid off during Alitalia's painful restructuring at the end of the last decade, with further redundancies coming on the back of more recent closures or mergers of Italian carriers.
Along with the cabin staff union, Avia, the IPA is calling for civil aviation regulator ENAC to compile a list of unemployed pilots and flight attendants to aid their search for jobs.
Galiotto blames ENAC for the sector's problems, citing a lack of regulatory oversight of Italy's air transport industry. The light touch approach led to carrier numbers ballooning to 20 airlines at its peak, the highest number of carriers in the European Union, he said.
"The question we should ask is why the regulatory agencies permitted that [growth] - why did they not check the financial status of the stakeholders and what are they doing at the present time to avoid this happening again in the future?" he asked.
ENAC on 31 January ordered an urgent check on the financial health of Italy's airlines. However, Galiotto believes it is too little, too late.