Licencing

I'm thinking about doing some recolors on an airliner on ecardmodels. I have a question about licencing though. I looked through Sumato's 767 and 777 threads, and I saw that he couldn't do some (like KLM) due to licencing problems. How do I avoid such problems? Are there certain airlines I can't do without paying a ton of money? Are bankrupt/old liveries exempt from licencing? If you guys could help me out with this issue, it would be greatly appreciated. Thanks!