Passengers with a canceled flight are entitled to a new flight on the same day of travel if it is available.
This is the case even if the only available flight is on a competing airline.
Passengers whose flight was canceled promptly may be entitled to cash compensation.
The compensation varies depending on the distance of the canceled flight and must be a minimum of £220.
This week, the government ordered airlines to cancel flights in July and August now to avoid last-minute chaos.
The letter is said to have been mainly addressed to easyJet due to the airline’s last-minute cancellations.
However, TUI, Wizz Air and British Airways have also canceled flights as they struggle with staff shortages.
An easyJet boss said the security clearance took too long and trained staff were still unable to get to work.
Rory Boland, editor of Which Travel? said of the cancellations: “Some holidaymakers have been notified the day they were due to travel, which is totally unacceptable.
“We continue to hear of examples of the airline failing to fulfill its legal obligations to passengers and ignoring their rights.
“If a flight is canceled within 14 days of departure, passengers may be entitled to compensation and should be given the option of being rerouted with another airline if necessary.
“We know that this requirement is not always met, so the government and civil aviation authority must intervene where airlines play with the rules quickly and loosely.”