I don't know about the long term projection but the Cost per Passenger Enplanement (CPE) is a factor in the recent CLT expansion.
Article dated May 2009
There's no doubt Pittsburgh's fees are high. The cost per enplanement to the airlines operating out of the airport, an industry benchmark, is $15.80, on average. While that will drop to $13.40 in June, it's still higher than the median of $6.24, based on 116 airports rated by Moody's Investors Service.Even at $13.40, Pittsburgh's cost per enplanement rivals that in some larger markets, including San Francisco, New York's LaGuardia, and Boston's Logan, based on 2007 numbers.
It is higher than Denver, Chicago O'Hare, Los Angeles, Philadelphia, Minneapolis-St. Paul, Detroit, Phoenix, Atlanta and Charlotte-Douglas, which, at under $2, is one of the lowest in the country.Read more: http://www.post-gazette.com/pg/09151/973762-28.stm#ixzz13urbYKK0
Philly.....Article dated October 2010
In fiscal 2009, operating revenues continued to grow reflecting the expansion of the terminal infrastructure and the inclusion of Outside Terminal Area (OTA) revenues available for debt service. In FY 2009, the airport reported debt service coverage of 2.61x and 1.68x, respectively. In FY 2010, coverage is expected to remain strong but will decline to 2.38x and 1.47x, respectively, reflecting the softening of some non-airline revenue cash flows and the generally flat traffic trends. Similarly, the airport's CPE has been inline with previous forecasts ranging from $6.15 in fiscal 2007 to $9.60 in fiscal 2010. With the addition of the airport's CEP and additional terminal infrastructure, the airport's forecasts indicate CPE will increase to the $12-$13 range by 2016 - which is still competitive for an international gateway and hub airport. Under a stress scenario in which connecting traffic is decreased by approximately 30% in fiscal 2012, the airport's CPE climbs to as high as the $16 dollar range. While this represents a 40% increase over previous levels, management has indicated that carriers are on-board with the increase and there is has been no conflict receiving MII approval from carriers. In addition, Fitch believes the CPE is still competitive relative to peer airports with the additional leverage.