I believe that Easy jet will be recruiting women under a positive action scheme. To my certain knowledge, in the past, HSBC and the BBC have gone down this route to redress the racial inequalities of their workforces. That is why we see and hear black and minority ethnic groups more and more in the BBC these days. The yardstick used is the number of a particular group in the background population.
We alll know the percentage of women in the population so that 50% or thereabouts will be the position they are aiming for.
Positive action schemes are lawful while positive discrimination is unlawful. Btw, the correct terminology is unlawful not illegal. The former is civil law while the latter is criminal law.