New Delhi: Cash-strapped Kingfisher Airlines got into more turbulence on Thursday by cancelling over 30 flights for the fourth consecutive day even as some pilots and cabin crew did not turn up for duty by reporting sick.

Thousands of passengers across the country were inconvenienced by the cancellation of flights and in some cases paid a premium of 20-40 per cent to travel by other airlines.

Over the past four days, the Vijay Mallya-owned airline has cancelled more than 120 flights maintaining they were taking some aircraft off their schedule to add business class seats in them.

Airline sources said 30-odd pilots and cabin crew have not reported for duty in the past few days on grounds of sickness, but discounted reports that 100 pilots had quit the airline recently. The payment of October salary and allowances of the airline staff has been delayed.

The airline has suffered a loss of Rs 1,027 crore in 2010-11 and has a mounting debt of Rs 7057.08 crore.

Kingfisher's flight schedules have also been severely hit with three oil companies -- HPCL, IOC and BPCL—stopping granting credit to it for lifting jet fuel and asking it to make payments on a daily basis.

Industry sources said the airline has grounded eight of its leased turboprop ATR aircraft.

The cash-strapped carrier also has unpaid dues to the operators of airports and other agencies, which have been putting pressure on it.

The Directorate General of Civil Aviation (DGCA) had on Wednesday issued a show-cause notice to Kingfisher asking why it had not taken the regulator's prior approval to curtail its flight schedules as required by the Aircraft Rules, 1937.

Officials said the airline is yet to reply to the notice but added that a reply was expected in a couple of days.