“Fund their own security”? And how is that going to affect their bottom line? Companies that want to cut costs and ticket prices by skimping on expensive security searches would pose a threat to all of us.
Moreover, who cleans up the mess if their security precautions fail? If a plane blows up upon landing at an airport, it won’t be the airline that has to pay for the cleanup - it will be the taxpayer. Same with a plane flown into a building ... would American Airlines have been able to assume all the costs of the WTC attack? They would just have reorganized under bankruptcy laws and walked away from the mess.
It would be very intriguing, though, to see how successful an airline which boasted “No onerous s3wecurity lines and searches!” did in attracting customers.