There is more uncertainty ahead for Britons planning to fly.
UK airlines have now been told to cancel flights they can't deliver this summer to stop a rerun of recent travel chaos.
The Government and the aviation regulator wrote to carriers on Tuesday telling them to ensure their summer timetables were "deliverable".
They added that earlier cancellations were "better" than axing flights at the last minute.
The BBC says this comes after tens of thousands of passengers have been affected by cancellations and delays at airports.
The problem was particularly bad during Easter and last month's half-term school holiday - and British Airways, TUI and easyJet have apologised.
Staff shortages have been blamed, after thousands of airline jobs were cut during the pandemic and have yet to be replaced despite a spike in post-pandemic travel demand.
In their joint letter, the Department for Transport and the Civil Aviation Authority set out five "specific expectations" for the sector.
They wrote: "We think it's important that each airline reviews afresh its plans for the remainder of the summer season until the end of September to develop a schedule that is deliverable.
"Your schedules must be based on the resources you and your contractors expect to have available, and should be resilient for the unplanned and inevitable operational challenges that you will face.
"While cancellations at any time are a regrettable inconvenience to passengers, it is our view that cancellations at the earliest possibility to deliver a more robust schedule are better for consumers than late notice on-the-day cancellations."
The letter stated that airlines must "keep consumers informed" about their rights during disruption, such as having "sufficiently staffed call centres and user-friendly digital channels".
It also urged airlines, ground handlers, air traffic control and the Border Force work more closely to try to prevent problems.
Airlines and unions told MPs on the Commons Business Committee on Tuesday that the staffing shortages blighting the industry were likely to persist this summer.
Oliver Richardson, national officer for civil air transport at the Unite union, told MPs it was unlikely the situation would be fixed "unless we work together".
Representatives from BA, easyJet and ground handling firm Swissport said they also faced long delays to get security clearance for new staff.