TOareaFan
Superstar
If Porter folds, any airline could take over operations and fly any jet that can be landed at the airport. Other airlines might not use the quiet jets Porter is touting to get expansion approval.
That's why it makes sense to regulate noise levels rather than technology. There are prop planes that make more noise than the Q400s so you could have the exact senario now....Porter could fold and someone could come in with noisier planes and take the slots...but as long as they are props then that is ok.
If you set noise levels and say any plane below that level of noise (that can safely land on the runways) can come in then you have dealt with that issue.