The Directorate General of Civil Aviation has suspended six pilots who had said their flights were low on fuel while landing at the Kolkata airport on November 30, The Times of India reported. Their de-rostering follows allegations made by West Bengal Chief Minister Mamata Banerjee’s Trinamool Congress members that a fuel shortage faced by the IndiGo flight she was travelling on was part of a plot to kill her.

The directorate has grounded two pilots each from IndiGo, SpiceJet and Air India, according to the report. Banerjee was on board the IndiGo airline, while the two other aircrafts were scheduled to land before her flight did.

Unidentified officials told the English daily that the move aimed at warning airlines against trying to cut costs on fuel expenditure, particularly during the winter when rescheduling or hovering orders are at their highest owing to fog and other factors. An Air India spokesperson said the DGCA has sought the “corrective training” of the pilots concerned. Spicejet confirmed the development.

Airlines are directed to store extra fuel on every flight in case of orders to hover or land at another airport. On December 1, domestic airline IndiGo had said that a flight carrying Banerjee on November 30 was never low on fuel, and had landed with more than the minimum diversion fuel. IndiGo had said it was a case of miscommunication between the pilot and the air traffic controller.