Jan 22 (Reuters) - India's IndiGo warned of higher per-passenger costs for the full year on Thursday, and said it took a $63 million hit in the third quarter following one of the country's worst-ever aviation crises.

The airline's quarterly profit plunged 75% to 6.13 billion rupees ($66.9 million) due to a one-time charge related to disruptions that forced the firm to cancel thousands of flights in early December due to poor roster planning.

The country's largest airline now expects its unit costs, the average cost of flying an aircraft seat, to grow in the mid-single-digit percentage range for the year ending March 2026, compared with an earlier projection of no rise in costs, Chief Financial Officer Gaurav Negi said on a post-earnings call.

IndiGo is relying on damp-leased jets to meet demand, CFO Negi said, as several jets remain grounded due to Pratt & Whitney engine issues. The arrangement is expected to increase costs.

Under a damp lease, IndiGo provides the cabin crew, while the jet and pilots are provided by the lessor. 

UNDER INCREASED REGULATORY SCRUTINY

IndiGo is facing a competition probe and increased regulatory scrutiny. India's aviation regulator curtailed the carrier's domestic capacity by 10% for the winter schedule, while warning its senior executives and fining the firm earlier this month.

Asked whether IndiGo's board had discussed accountability at the CEO level following the disruptions, CEO Pieter Elbers said, "The board has its own deliberations."

DEPRECIATING RUPEE DRIVING UP EXPENSES

Over 60% of IndiGo's costs are directly or indirectly dollar-denominated, and a depreciating local currency is driving up overall expenses for the company.

IndiGo, which commands nearly two-thirds of the country's aviation market, saw its quarterly revenue grow 6%, but expenses rose at a faster pace, rising 10%. 

Dollar-denominated supplementary aircraft leases, the airline's second-largest expense, jumped 19%.

The carrier took a one-time charge of 14.67 billion rupees in the quarter, including 5.77 billion rupees for disruption-related costs such as passenger refunds and a fine by the regulator. The remainder of the charge was due to India's recently enacted labour code.

IndiGo also expects fourth-quarter capacity - measured in available seat kilometres - to grow 10%, while unit revenues are expected to decline by an "early-to-mid" single-digit percentage.

($1 = 91.6090 Indian rupees)

(Reporting by Nandan Mandayam in Bengaluru and Abhijith Ganapavaram in New Delhi; Editing by Nivedita Bhattacharjee)