India’s Supreme Court this week stuck by its 1998 decision to force buses in Delhi to convert from diesel to natural gas, but extended the deadline for the switchover by six months, until the end of September. The court added a caveat, however: Bus operators can only take advantage of the extension if they can prove by Saturday that they intend to meet the new deadline. The court’s moves came in response to complaints by the Delhi government, which said it would not be able to convert its 2,000 buses by the original deadline of the end of this week. The Tata Energy Research Institute said that it is unlikely that the city or private bus owners, who operate about 10,000 of the vehicles, will be able to convert all the buses by September.