Britain's air traffic control systems were hit by a technical fault on Monday with airlines and airports warning of flight delays and possible cancellations.

"We are currently experiencing a technical issue and have applied traffic flow restrictions to maintain safety," the National Air Traffic Services (NATS) said.

"Engineers are working to find and fix the fault," it added.

NATS did not provide details on what caused the issue or how long it will to take to resolve. 

It clarified that the UK airspace was not closed.

The issue comes on what is expected to be a busy travel day with Monday a public holiday in parts of the UK. 

"We are aware NATS is currently experiencing a technical issue. We are seeing delays, and cancellations are likely," London's Gatwick airport said.

Heathrow, the UK's biggest and busiest airport, said that "as a result of national airspace issues there is disruption to flights across the UK" and advised passengers to check with their airline for the latest updates.

A British Airways flight from Malta to London Gatwick was delayed by more than three hours on Monday afternoon and an Air Malta flight set to depart Malta at 5pm has been delayed, according to the Malta Airport website. An Easyjet flight to Malta from Gatwick was cancelled and a Jet.Com flight from Stanstead was delayed.

British Airways said it was "working closely with NATS to understand the impact of a technical issue that is affecting UK airspace" and will keep its customers updated.

Budget airline Ryanair, which mainly flies across Europe, said that it will be "forced to delay/cancel a number of flights" to and from the UK on Monday.

Scottish airline Loganair meanwhile said that there has been a "network-wide failure of UK air traffic control computer systems" on Monday morning and warned of flight delays.