Use a padded board bag. Bubble wrap the board with cardboard around the tip and tail and if you have room stuff some of your clothes in to the bag as well. Usually there is a charge for the board so you can prevent an excess baggage fee this way.
If they don't x-ray the unit at the counter you can say it's just personal effects and no board is there or it's broken so not a useable one...
(not technically a board any more so how can they charge you???)
Bring a ding kit and tape anyway and don't say anything about it as it may be considered d.g.'s.
Avoid Skyservice Airlines out of CYYZ. They mashed my board completly. Besides the shoddy baggage service, they occasionally bend their airplanes on landing. Tons of dents on my board and the nose got dinged pretty badly even though it was packed really well.
Paddle proud.