India's struggling Kingfisher Airlines was forced to cancel more than 30 flights Wednesday when pilots and engineers refused to show up for work due to non-payment of salaries.

The cancellations were a fresh blow to the debt-laden airline which has been hit by a series of similar strikes in recent months and owes vast sums to banks, suppliers and staff.

Around 22 flights originating in New Delhi were cancelled, along with nine from India's financial centre Mumbai.

An airline spokesman declined to comment on the latest stoppage, but a Mumbai airport official said Kingfisher had cited "operational reasons" for the cancellations.

"For the past five to six months, the airline is defaulting on paying us salaries, despite several promises," said a junior Kingfisher pilot who declined to be named.

"How long can one work without being paid?" the pilot said.

Kingfisher, which has $1.4 billion in debts, has been forced to slash its fleet of aircraft and has halted international operations in an effort to curb costs.

It now has the smallest market share among Indian airlines at 4.2 percent, after being the second-largest carrier at its peak.

A quarter of Kingfisher is owned by local banks and some have refused to lend the company more cash unless fresh capital is raised.

In May, the airline reported quarterly losses tripled to 11.52 billion rupees ($210 million) from a year earlier.