The new airline will start flying on October 15, after receiving the green light from Italy's civil authorities last week, with tickets going on sale on August 26, ITA announced in a statement.
Alitalia meanwhile said that from midnight Tuesday it will stop selling tickets for flights from October 15, with customers who have already booked after that point able to change to an earlier flight or receive a refund.
The airline stated on social media that it would send a "direct communication" to all customers with further instructions.
Italy's Corriere della Sera newspaper estimated that some 255,000 people have tickets booked with Alitalia after that date.
The board of directors of ITA meanwhile made a binding offer to buy 52 of Alitalia's aircraft, as well as airport slots and other assets.
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Loss-making Alitalia was placed under state administration in 2017 but Italy has struggled to find an investor to take it over. The situation was only exacerbated by the coronavirus pandemic that grounded airlines worldwide.
Earlier this year Italy said it had reached an agreement with the European Union for a bailout that creates a new debt-free company to take over some of Alitalia's assets.
The Italian government has created a 100-million-euro ($117-million) fund to reimburse Alitalia customers.
An Alitalia plane sat on the tarmac at Milan's Linate airport. Photo: GIUSEPPE CACACE/AFP
ITA’s scheduled debut comes amid serious challenges for the airline industry that was battered during the coronavirus pandemic, especially larger carriers already struggling to compete against low-cost airlines.
ITA has indicated it will make Rome Fiumicino its main international hub, with Milan Linate its second-biggest airport.
Its preliminary business plan includes 61 routes in 2021 to 45 different destinations, chiefly other European capitals including Paris, London, Amsterdam and Brussels.
Its long-haul routes will focus on major airports in the United States and Japan, including New York, Boston, Miami and Tokyo.
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It will also fly domestically between 21 airports in Italy, allowing people travelling to or from smaller airports such as Venice, Genoa, Verona, Florence, Naples and Bari to connect to international flights in Rome or Milan.
By 2025 the airline hopes to add nearly 30 new destinations, including Washington DC, Los Angeles, Sao Paolo and Buenos Aires.
It has said that it aims to become “the first choice on international destinations to and from Rome Fiumicino".