Which country pioneered the use of algae-based biofuel in commercial aviation?

 title: 'New EU-funded FUELGAE project aims to resurrect algae as a promising source for aviation biofuels'

The United States pioneered the use of algae-based biofuel in commercial aviation. In January 2009, Continental Airlines conducted the first-ever commercial jet test flight partially powered by a fuel made from oils derived from algae and the non-crop plant jatropha[2][5].

This project showcased algae's potential as a sustainable aviation fuel source at that time. Despite early promise, the use of algae-based biofuels faced challenges in scaling up production and achieving economic viability, leading to a temporary decline in interest and investment[6].