The government is reviewing airlines' decision to charge passengers for selection of any seats during web check-in as it looks to ascertain whether the move violates existing rules.

Replying to a customer's query on Twitter on Monday, SpiceJet said that "pre-allocation of seats through web check-in is on chargeable basis".

No-frills airline IndiGo is the largest domestic airline with a market share of nearly 43 per cent in October and its announcement on Sunday through Twitter triggered concerns, with many users of the microblogging site raising questions.

Against this backdrop, the ministry said it would review the decision.

"MoCA has noted that airlines are now charging for web check-in for all seats. We are reviewing these fees to see whether they fall within the unbundled pricing framework," the ministry said in a tweet.

When asked whether the Directorate General of Civil Aviation (DGCA) was looking into IndiGo's decision to charge for all seats at the time of web check-in, a senior official of the regulator replied in the affirmative.

"Yes, as per our regulations," he told PTI.

With unbundled pricing framework, airlines are allowed to charge for various services, including for booking extra leg-room seats.

Under IndiGo's revised policy, all seats are chargeable for web check-in. "Alternatively you may check in at the airport for free. Seats will be assigned as per the availability," the airline said in a tweet on Sunday.

By way of web check-in, passengers verify their presence on a flight online and seats can also be chosen.

Generally, IndiGo passengers can choose certain seats free of cost while making the selection online.

In a two-page statement issued on Monday, IndiGo claimed it has "neither changed its web check-in policy nor is there any charge for web check-in".

While noting that customers would not compulsorily have to pay for the seats, the airline also said the pricing is only for advance selection of seats.

"When the customer checks in at the airport, the seats would be assigned for free... Advance selection for a small fee helps consumers reserve the seat of their choice on their flight," it said.

If the passengers have no particular preference for seats and would not like to pay for advance seat selection, they can either reserve any free seats available at the time of web check-in or will, of course, be assigned seats at the time of airport check-in, the airline said in the statement.

When contacted, an airline spokesperson did not provide any clarity about contradiction between Monday's statement and Sunday's tweet.

In Monday's statement, IndiGo said that 'advance selection' segmentation is based on consumer preferences and market demand.

"IndiGo customers will not compulsorily have to pay for the seats... this is a common practice followed by airlines across the globe," it noted.

The airline said there is no change in the airline's web check-in practice but makes dynamic decisions about pricing for 'Advance Seat' selection.

"While the preferred seat pricing starts as low as Rs 100, there would be some seats that may be available for free depending on the market dynamics for the flight.

"Thus, there are some seats that are available for free at a certain time period before departure (e.g. one day before departure) or on certain aircraft type (e.g. ATR operated flights)," the statement said.

Meanwhile, replying to a customer's query on Twitter on Monday, SpiceJet said that "pre-allocation of seats through web check-in is on chargeable basis".

"If a passenger does not wish to pay for a seat, he/ she may request for a preferable seat while check-in at the airport. Our team shall provide the seat without charges, if available," the airline said.

This was in response to a tweet saying that web check-in at SpiceJet is chargeable, as check in not allowed without booking seat.

There was no statement from SpiceJet about its web check-in policy.

Grappling with spiralling operational costs, airlines have been looking at ways to increase their revenues from ancillary services. In the latest September quarter, all the three listed carriers -- IndiGo, SpiceJet and Jet Airways -- were in the red.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)