Bringing some respite to air travellers' pockets, the country's civil aviation regulator director general of civil aviation has asked airlines not to charge passengers for booking their preferred seats in advance.

"I have asked the airlines not to charge passengers if they book their preferred seat in advance. The order has been issued and the airlines would comply at the earliest," DGCA E K Bharat Bhushan told PTI.

The DGCA had issued a letter to the airlines on July 15 which said, "All the scheduled domestic airlines are directed to withdraw such charges with immediate effect under intimation to this office... Any mention about the same on the website may also be deleted on an immediate basis."

Low-cost carriers SpiceJet, IndiGo and GoAir as well as Air India Express -- the low-fare international subsidiary of state-owned Air India -- allow passengers to block the seat of their choice for an extra charge while booking tickets on their websites.

The DGCA, since November last year, has made it mandatory for domestic airlines to submit an advance fare with details of minimum and maximum tariff on the first day of every month and also publish the fares on their websites.

The letter said airlines were violating these guidelines by charging passengers for booking particular seats.

"Some airlines were charging this amount for the entire seat inventory, which is contrary to the provisions of rule 135 of the Aircraft Rules, 1937, contained and totally unjustified," the letter said.

GoAir and SpiceJet charge Rs 50 for any seat selected online. IndiGo charges Rs 400 for front row and emergency row seats and Rs 50 for all other seats in domestic flights while on international flights, it charges Rs 750 for front row and emergency row seats and Rs 150 for all other seats.

Air India Express charges Rs 300 for front row and emergency row seats and Rs 100 for all other seats.

Of the foreign airlines, low-cost carrier AirAsia charges about Rs 450 for front row and emergency row seats and also allows priority boarding to passengers while British Airways charges USD 15 for similar seat booking.

Seats in the front and emergency rows are generally preferred as they offer more legroom.