Thomas Borchert writes:

Read them (again)!

Reading them again will not change what they say.

He is not required to understand general English, he is required to understand
aviation English and standard phraseology.

There is no difference between the two, unfortunately.

This is similar to the illusion that there exists a "business English" that is
somehow easier to learn than standard English. In fact, there is no such
thing--English is English--but language schools promote the illusion because
it brings in more customers (who mistakenly believe that they can get away
with learning something "simple" instead of standard English to communicate).