Continental Airlines said a blend of biologically derived fuel and jet fuel performed slightly better than jet fuel alone during a test flight by the world's fifth-largest airline.

During some parts of a 90-minute test flight in January, the blended fuel displayed a 1.1 percent increase in fuel efficiency over traditional jet fuel alone, the Houston, Texas-based airline said in a statement on Wednesday.

Continental estimates greenhouse gas emissions were cut at least 60 percent by using the blend.

Airlines have been exploring alternative fuel sources for years in an effort to counter volatile fuel prices. Jet fuel rivals labor as the top cost at most major airlines.

In January, Continental test pilots took a Boeing 737-800 that had one engine operating on jet fuel and the other operating on a blend of biofuel and traditional fuel.

The biofuel blend consisted of oil derived from algae and jatropha plants. The algae oil was provided by Sapphire Energy and the jatropha oil was provided by Terasol Energy.

(Reporting by Deepa Seetharaman; Editing by Tim Dobbyn)