For the first time in history, an alternative jet fuel has been cleared for landing.

United Airlines will test out a 70/30 biofuel combination of regular jet fuel and animal fat and farm waste on a flight from Los Angeles to San Francisco. The roughly hour-long flight is set to take off this summer, according to The New York Times. The biofuel will be supplied by AltAir Fuels, from which United bought 15 million gallons over a span of three years.

The company plans on phasing in the biofuel into four or five flights per day for two weeks with plans on integrating the fuel to all flights thereafter. The Times also reports that United will invest $30 million into Fulcrum BioEnergy, one of the largest producers of biofuels for planes.

Not only is this a step forward in terms of decreasing air pollution, but the cost of biofuel is also lower than that of traditional jet fuel: less than $1 per gallon as opposed to the $2.11 United is paying on average.

Southwest Airlines plans on using biofuel made with wood residue by next year, while Alaska Airlines set the goal of using an alternative fuel at one of its airports by 2020.