Travellers face airport delays if Britain's airspace design is not updated, the UK's air traffic control company warned on Friday, at the start of a record-breaking summer flights season.
"The ageing design of UK airspace means we will soon reach the limits of what can be managed without delays rising significantly," Jamie Hutchinson from NATS, formerly known as National Air Traffic Services, said in a statement.
A record-breaking 8,800 flights were scheduled to depart from the UK on Friday and more than 770,000 overall during the summer, also a record.
The season figure was 40,000 more than 2016.
The Department for Transport estimates that if the airspace remains unchanged, there will be 8,000 flight cancellations a year.
The rise in delays and cancellations would not only inconvenience passengers, but also damage the wider economy, NATS said.
Plans to expand several British airports are already under way.
On Friday, work started at Manchester airport as part of a £1 billion ($1.3 billion, 1.1 billion euro) programme to double the size of its Terminal 2.
The government has also backed the creation of a new third runway at London's Heathrow airport, but the decision has met with strong environmental opposition.
Of the record 2.4 million British holidaymakers expected to travel overseas this weekend, more than 1.4 million will fly.
But the ports and the channel tunnel will also be "extremely busy", the UK's largest travel association ABTA warned, with 58,000 passengers heading to Paris or the South of France on Eurostar.
The Mediterranean region is particularly popular with British holidaymakers, although their favoured destinations have changed.
Spain, Italy and Portugal now top the list that Egypt, Turkey and Tunisia once did, partly as a result of security concerns.
Thirty Britons were killed by an Islamist gunman in an attack on a hotel in the Tunisian resort town of Port El Kantaoui in June 2015.
