British Airways (BA) has cut fares by up to 50% to more than 65 destinations across Europe, as it aims to win back more passengers from budget rivals.
The airline said the move would affect about seven million seats a year and was "not a short-term gimmick, but a long-term commitment".
Yet some analysts said it was typical for BA to cut ticket prices ahead of the key summer holiday season.
BA also said it was scrapping all non-changeable economy tickets.
Passengers will instead now be able to change their flights up to midnight the day before departure, no matter what they have paid for the ticket.
The advertised fares will continue to include all taxes and fuel surcharges, but there is a £15 charge for passengers who do not book online.
BA will also continue not to charge extra for food and drinks, unlike some of its low fare rivals.
"We operate in a very competitive market and are determined to be the first choice for air travellers who want low prices, flexibility and a superb flying experience," said BA commercial director Martin George.
BA added that there would be no job losses as a result of the price cuts.
Nick van den Brul, an analyst for French bank Exane BNP Paribas, questioned the price cuts.
"They [BA] typically do this at this time of the year as we enter the summer and holiday season on their European routes which are the most competitive and price-vulnerable to competition from Easyjet and Ryanair," he said.
Low-fare rival Ryanair, meanwhile, dismissed BA's move.
The airline's deputy chief executive Michael Cawley said BA had to be "more honest and transparent with its pricing, and stop supplementing its already-high fares by hitting passengers with £35 fuel surcharges".
"Ryanair's fares are still only a fraction of BA's - even with their so-called fare 'shake-up'," Mr Cawley said.
BA said its one-way fares within the UK and Europe have now fallen by an average 70% over the past decade.
Its latest announcements come after the airline unveiled new fuel surcharges on long-haul flights.
On Tuesday the airline increased its fuel surcharge on long-haul flights sold in Britain to £35 from £30 per one-way ticket, the first time it has increased the levy since September.
The airline said the increase was "regrettable" but necessary because of the high price of oil.
BA said the fuel surcharge for its short-haul flights would remain at £8 for a one-way ticket, and £16 for a return trip.