India, Oct. 29 -- A small, single-propeller aircraft operated by IIT Kanpur crisscrossed the overcast skies above northwest Delhi and parts of the National Capital Region on Tuesday, firing silver iodide flares in two cloud seeding trials that failed to produce rain-even as the capital's environment minister hailed the exercise as "successful".

The aircraft fired 16 flares-eight in each trial-containing silver iodide and sodium chloride compounds over Burari and surrounding areas, Mayur Vihar, and Noida in attempts to induce rain in a much-debated plan to tamp down air pollution that tends to accumulate this time of the year.

"Delhi has taken an unprecedented, science-first step by adopting cloud seeding as a tool to control air polluti...