Heathrow airport in London has called for "an honest conversation" about expansion after another record month for passenger numbers.
More than 7.2 million passengers travelled through its terminals last month.
This was up 0.4% from a year ago and represents its busiest May on record.
A Heathrow spokesperson said: "As these record numbers become the norm, it's time to start an honest conversation about the challenges this presents for an already space-constrained yet highly efficient hub".
"Heathrow continues to deliver excellent service, but to sustain this performance and meet future demand, expanding capacity will be essential," the spokesperson added.
The airport has previously said it will submit detailed plans for building a third runway to the UK government in the summer.
Chancellor Rachel Reeves used a speech on growth in January to give her support to the project, which has been repeatedly delayed over several decades because of environmental concerns.
