Are you thinking about flying with marijuana? Maybe you've already done it. I know a lot of people that have flown with marijuana for a very long time. I know even more people that have thought about doing it, but were obviously worried about the possible ramifications.
I once flew from Portland to Denver with a very prominent marijuana figure who flew with a quarter pound of flower and an ounce of concentrates. I went through the security check and didn't have any issues. The person I'm talking about was right behind me, and was stopped.
For obvious reasons, my heart was pounding wondering what might happen to him. After a brief discussion with the TSA employee, I saw him reach into his bin of stuff, pull out his keys, pull a very small pocket knife off of his key chain. He then proceeded forward through the checkpoint. When his carry-on bag - with the cannabis in it - was run through the x-ray machine, I could clearly see the flower and concentrates which were in vacuum sealed bags. Yet, the TSA guy didn't bat an eye. This, of course, was a flight from Portland to Denver, so he probably just didn't care.
What you should know about flying with marijuana
But what about other airports? What is their protocol when they come across marijuana? One big misconception is that the TSA people are cops - which is not the case. They do security work, but when a crime is found to have potentially occurred, they detain the suspect and call local law enforcement. So if you are flying out of Seattle's airport, for instance, Seattle police would be called, who would be enforcing Seattle laws. So if you are flying out of a legal state, you can fly with whatever your state's legal medical and/or recreational marijuana limits are.
But there are some exceptions. Denver's airport for instance has a law specifically against flying with marijuana, but they also have amnesty boxes where you can drop off your marijuana without any questions being asked. Realize that not all airports and local cops are created equal. The cops in Portland, Oregon, where marijuana is legal, are going to be far nicer if/when they come to the airport to investigate compared to cops in Louisiana (where marijuana is still very much illegal).
The moral of the story is if you can avoid flying with marijuana, that is always best. But if you do, chances are you will likely be successful, but there will always be the risk of getting busted if you are flying from or to a state that does not have legal recreational or medical marijuana laws.