An investigation by the CAA has found no compliance breach by air traffic controller NATS (En Route) Plc.
The investigation, under the Transport Act 2000, came after complaints from Ryanair and London Stansted Airport.
The pair had alleged that the ATC operator, known as NERL, had failed to provide adequate resources and had discriminated against traffic landing at Stansted.
Although the CAA found no compliance breach, it found areas for improvement to NERL’s business practices.
These include improving the resilience of its operations and contingency planning.
"This is the first time that the CAA has used its investigatory powers under the Transport Act 2000 and highlights the potential seriousness of the complaint raised," said Richard Moriarty, director of consumers and markets at the CAA.
"In this instance, our investigation has found no compliance breach, however improvements to operational resilience are key to ensuring service delivery levels are maintained in our increasingly busy airspace."
The CAA said it would also increase its own oversight of NERL to address resilience issues.
