Mark
You may not like it but benhurr is giving good advice there. As a group, pilots have lower Verbal Reasoning ability (which includes spelling), so you are not alone! This is characteristic of a group with higher technical ability, however, if you know you have a weakness it is vitally important that you do something about it and not just accept it. This will speak volumes to a potential employer, or rather the lack of doing something about it will!
As a general bit of guidance to all job seekers, get a few books from the library about grammar, spelling, punctuation and general use of the written word. It also provides a good talking point when asked at interview "what are your weaknesses?"
The important thing is to have DONE SOMETHING about your them!
Good luck.
PP
ps, not proof read my own post for spelling and grammatical errors as I have a job thank you very much!