In the 1980s, after-dinner speaker David Gunson, a former air traffic controller, humorously observed that as the worlds skies became more congested, so arose a need for air traffic control - who went on to justifying their existence even further by forcing aircraft together and down narrow corridors of airspace known as airways, thus increasing the risk of collision. To some degree David was right; structured corridors - especially those in busy crossroads - are often in demand, and usual separation criteria cannot be maintained without implementing flow control, resulting in the much more familiar 'summer holiday flight delays caused by air traffic control'. While the airports themselves are a harder and more expensive problem to solve,for which there is little better solution than to increase the number of runways, there is still quite a lot of useable space outside of the existing airways structure.
The strategic plan by Eurocontrol is Free Route Airspace (FRA), which in its simplest form allows operators to fly more direct point-to-point routes, as opposed to being forced down a rigid structure of airways. Why hasn't this been done before? Much of it comes down to technology, which has allowed for increasing traffic volume and density. As well as advances in air traffic control integration, the technology onboard aircraft has advanced so as to allow pilots both to navigate far more accurately and autonomously using satellite-based navigation, as well as being made aware of conflicting traffic by making use of other flight deck systems, such as Traffic Collision Avoidance System (TCAS) - with many of the new technologies mandatory to fly in high density airspace.
While passengers should benefit from shorter flight times, as tracks become more direct, the environment will benefit too. Romania has been operating FRA since 2013, followed more recently by Italy and end of 2016.