In Williams v British Airways plc [2010], Case C‑155/10, the Advocate General confirmed that in circumstances where there are no specific rules as to how annual leave should be calculated (either in the Working Time Regulations 1998 or in any relevant agreement), paid annual leave should correspond to the average earnings of those workers, including any other consideration, whether in cash or kind, which the workers receive, directly or indirectly, in respect of their employment.

The workers in question were pilots for British Airways, for whom the applicable regulations and collective agreements were silent on how to calculate their rate of pay for statutory holiday purposes. The Supreme Court held that the holiday pay should not be limited to basic fixed pay only but should include any normal additional flying allowances.

On referral, the Advocate General confirmed that the correct position is that holiday pay should ‘correspond' with a worker's normal remuneration, including any other consideration normally received, e.g. bonuses, ex gratia payments and supplements or allowances for mobility, overtime and shift work.