European and American carriers have been testing a new program to make transatlantic flights greener this week, and while travelers may not have noticed it, the scheme could make a big difference.

Passengers on board Air France flight AF690 from Paris to Miami on April 6 probably didn't notice anything out of the ordinary, but they were on a ground-breaking flight. As the first transatlantic crossing flown under the new Atlantic Interoperability Initiative to Reduce Emissions (AIRE) program, flight 690 marked an important moment for aviation.

Some of the key aspects of AIRE are rather simple. On the ground, for instance, the taxiing time for the jet was reduced at both ends to save fuel, and pilots reduce the engines used (aircraft taxi using their jet engines, which is very inefficient).

As the most efficient altitude to fly is determined by the weight of the aircraft, air traffic controllers along the route (from France, the UK, Portugal, Canada and the US) allowed it to climb slowly and continuously as fuel was burned, maintaining the "greenest" altitude. It took an optimized route over the Atlantic, and used a "continuous descent" approach into Miami, maintaining the same trajectory to save fuel during the landing.

The result of these steps is that during the nine hour 30 minute flight, the Boeing 747 used two to three fewer tonnes of jetfuel than it normally would. By the time it taxied onto the stand at Miami International at 14:45, it had produced between six and nine tonnes less carbon dioxide than a normal flight.

According to estimations by the ICAO's flight carbon calculator, the flight would normally produce around 192 tonnes of carbon dioxide. So while a reduction of between three and five percent (theoretically) doesn't sound earth-shattering, it's certainly a start. And for those on the ground, there was certainly a big difference - during the departure and arrival phases, Air France says that it more than halved noise levels

Air France estimates that if the AIRE system was implemented on all of its transatlantic flights, the savings would stack up to 135,000 metric tons a year. With more carriers joining the program, that figure can only grow. On April 7, an American Airlines 767 jet flew the same route using the AIRE procedures.

The airlines are now working with air traffic controllers, airports, the US Federal Aviation Administration and the European Commission to study the results and how best to implement the next steps of the AIRE program.

As the first large-scale environmental initiative bringing together aviation players from both sides of the Atlantic, AIRE could be an important step forward in making aviation greener.