Philadelphia International Airport (PHL) is a regional hub with frequent domestic flights from all over. Car rental franchises abound at PHL. From PHL it is a 60 minute drive to Stowe in the middle of the night; it is as much as 2-1/2 hours during rush hour. A SEPTA train "Airport Line" runs between PHL and 30th St. Station in Philadelphia. Look at the 'Public Transportation' link if you would like to consider this option.
A much more relaxing airport, albeit with fewer flight alternatives, is the Allentown/Bethlehem/Easton Lehigh Valley International Airport (ABE). Car rental is available, and the drive from ABE to Stowe is a much less hectic 60 minutes.