The Supreme Court has decided to refer the case of British Airways plc v Williams and others to the European Court of Justice. The pilots' argument that they should be paid not only basic pay, as was BA's policy, but also flying allowances when on annual leave, was accepted by the employment tribunal and the EAT but rejected by the Court of Appeal.

The Supreme Court has taken the view that the issue turns on what is meant by 'paid annual leave' in the Working Time Directive. While the Working Time Regulations 1998 establish a formula for calculating holiday pay, Regulation 18 expressly excludes certain workers in the aviation sector. Aviation workers have a separate entitlement under the Civil Aviation (Working Time) Regulations (which implements the Aviation Directive) to a minimum of four weeks' paid annual leave. However, unlike the Working Time Regulations, the Aviation Regulations do not state how the rate of pay for statutory leave should be calculated. The Supreme Court has decided that the pilots' case raises questions of interpretation of the Directives and has made a reference for clarification on their meaning.