We responsible gun owners make more mistakes than we would like to admit, even we aren't immune to forgetting things.
Is it negligent? Sure, this case can be made but it is not one or the other.
People forget things or are negligent in their actions all the time and unfortunately sometimes it results in serious consequences. There are people who are smart yet they forget their child in a hot car. Remembering or not remembering something is not a reliable indicator of whether someone is stupid.
So, now you're speaking for all responsible gun owners and admitting for us that we all make mistakes when it comes to properly transporting firearms?
Really?
I also don't think you understand the meaning of "negligence." You seem to have the "Hillary Defense" in mind.
When I know I'll be checking a gun in at the airport, I have it IN THE LOCKED CASE, and if small enough IN MY CHECKED BAG. It's unloaded, and ready to be declared.
If you wait until you're at the check-in counter, you're doing it wrong. Even if you're LE, there's little to no chance you'll need to use it from your home or hotel to the boarding gate. If it makes you feel better, and you have a car, do the prep work inside the vehicle, which gives you protection up until the moment you arrive at the airport.
Nobody should be clearing a loaded weapon at the check-in counter. That's too obvious.
Nowhere in that process is there an allowance for "I forgot I had my gun on me." If you KNOW you are traveling, and you KNOW you have to declare your firearm, there's no excuse for "forgetfulness." You prepare for checking it in and declaring it before you get there. Anything else is irresponsible.