Actually it's to indicate sponsorship. The pilot agrees to have a certain amount of money docked out of his paycheck and once it's passed a certain level, then he gets his name painted on the side of his chosen aircraft. It's a way for the government to reduce crippling defence costs.
You also noticed the rank painted there, That really indicates the level of contribution and was chosen as it seemed so much more professional than using Silver, Gold, Platinum etc.