"If you are a prior employee of Qatar Airways or any of its subsidiary companies, please include your employee number?" - What does this question mean?

This sounds like a question that is being asked on a job application form. Essentially what the interviewer is asking is were you were previously employed by Qatar Airlines or any sister companies of Qatar Airlines? 

For your reference you can find all of Qatar Airlines subsidiary companies on their website here

If you were employed with any of those companies, you would have been given an employee number on your contract of employment and probably any pay-checks you received, so this is what you will need to write on the application.

Help with filling in a job application

Need a bit of advice for the rest of your application with Qatar Airlines?

The video below has some great hints and tips to assist you when filling out a job application, plus some interview tips too! It's not for a specific job so worth a look no matter the job you are applying for.