This reply applies to any to country where you might work as a teacher:
You are fortunate to have found a job that offers you an airfare, in whatever form, whether a flat rate or based on the actual ticket price. Before accepting a job that promises airfare reimbursement, you should look closely at your employment contract to see under just what terms this is done.
Standard paper air tickets are being phased out this year by all major international carriers. Whatever purchase method you used to obtain your e-ticket, you will either have a sales receipt of some kind or a credit card statement. Some schools will not entertain a refund without it.
See how one school in Asia manages itsairfare refund