Calculate however you want right now. IMHO, the correct methodology is 2020 wages x 2020 raise. 2021 wages x compound raise for 2020 & 2021, 2022 wages x compound raise for 2020, 2021 and 2022.

This would be the math for 7% annual raises over 3 years.
7% x 2020
14.5% x 2021
22.5% x 2022

Assuming flat wages of 200,000 per year it comes out to $88,000 retro or 44% of an average year.

Two key factors are compounding the raises and applying it to all years of back wages that are owed to the pilots.