Britain will modernize its outdated airspace in a bid to make the aviation sector greener and cut the amount of fuel it burns by a fifth, the government said on Friday, on what could be the country's busiest-ever day for flights.

The Department for Transport (DfT) said that technology would be used to improve the efficiency of flight paths and speeds, and the changes could see planes reduce the fuel they burn by the equivalent of 400,000 fewer flights a year.

"We need to keep our infrastructure in the sky up to date to keep people moving," said Aviation Minister Charlotte Vere. "It hasn't fundamentally changed since the 1950s and, without action, one in three flights could face delays of half an hour or more by 2030."

"It is a complex and pressing task, but it will make flying cleaner, quieter and quicker as we make our aviation sector one of the greenest in the world," she added in a statement.

The DfT said that the modernization of Britain's airspace would help cut circular queues in the sky above busy airports as aircraft wait to land, known as stacking, helping to reduce carbon and noise.

Last month, activist group Extinction Rebellion disrupted London and have called for people to fly less. Travel firms like Thomas Cook have cited high-profile environmental campaigns as one factor reducing the demand to fly this year.

Intense competition between airlines has also created overcapacity, another factor putting pressure on the sector.

The DfT said that Friday could mark the busiest ever day for Britain's airspace, with over 9,000 flights, as soccer fans travel to Madrid for an all-English Champions League final between Tottenham Hotspur and Liverpool.