“The American people deserve an aviation system that can keep pace with our increasing reliance on air travel and NextGen will help us get there.” Source: FAA Acting Administrator Michael Huerta.
The desired time that an aircraft should cross a certain point (landing or metering fix). It takes other traffic and airspace configuration into account.
The stated mission of this site is to provide support for the sharing of aircraft through clubs, FBO's, flight schools, partnerships and corporate aviation departments.