From Appendix K "Resourcing and resilience" of the RP3 Business Plan
https://www.caa.co.uk/uploadedFiles/...D%20261018.pdf
"The combination of these factors, and the fact that the number of ATCOs retiring or leaving the business has exceeded our
expectations (for example through changes in pension tax legislation), means that we currently have around 30 fewer ATCOs than we
need to deliver a high quality service with the right levels of resilience. Between now and the start of RP3, we expect the numbers of
retirements and other losses to exceed the rate at which we can train new ATCOs, increasing this shortfall to around 50 ATCOs. Lead
times of three years on average to recruit and train new ATCOs, and up to a further two years to achieve the level of sector validations
of experienced controllers leaving the business, have made it challenging to meet the operational requirement. We have managed
this, and will continue to do so, through increased productivity and overtime, and through improvements to our training and selection
processes. However, this is not a sustainable position, and we need to ensure we can provide the required level of operational
resilience with even higher forecast traffic levels."