The UK's Civil Aviation Authority is enforcing legislation to make Aer Lingus, Wizzair and Jet2 change their compensation policies for delayed and cancelled flights.
The CAA intervened when it emerged the airlines were not paying compensation for flights disrupted by "ordinary technical faults", despite a court of appeal decision last year ruling carriers are legally obliged to do so in such circumstances.
The watchdog had threatened enforcement action against the airlines, but has withdrawn this after they agreed to alter their policies.
The CAA said it also had evidence that both Wizzair and Jet2 were imposing a two-year time limit, instead of six, on passengers making claims following disruption.
Hungarian airline Wizzair is still challenging this ruling and the CAA has referred the matter to the Hungarian Authority for Consumer Protection.
Jet2 has agreed to process compensation claims dating back six years and both it and Aer Lingus have now agreed to improve the quality of information they provide to passengers during disruptions and have signed legal undertakings confirming this.
Andrew Haines, chief executive of the CAA, said: "During the last year we've stepped in to make sure a number of major airlines change their approaches and improve the support provided to their passengers.
"The results of our recent action are a further boost for UK passengers and we are very pleased to see the changes the airlines involved have made. But our work is not done.
"We are determined to stand up for passengers and will continue to review how airlines are treating, and responding to, their customers in practice.
"Furthermore, while we recognise not every claim for compensation will be eligible, we are keen to hear from people who feel they have not been treated fairly and where we believe airlines are not complying with the law, we will pursue all available enforcement options."