It's unreasonable to expect even a frequent flyer to know exactly how one of these instruments should be filled out. To expect and occaisional flyer to know all the ins and outs, and what constitutes a "correctly completed MCO" is just plain absurd.
Seems like this system is ripe for abusing and defrauding customers.[/B]
The following is a link to the ARC website that teaches the ins and outs to travel agent's in the US how to properly fill out a MCO. Most of the theories apply to MCOs issued elsewhere or by an airline.
http://www.arccorp.com/forms/pp/iah5_6.pdf