Passengers will be able to reserve seats on Germanwings from May 1.
Thomas Winkelmann, ceo of the German low cost carrier, said the new service was being introduced at the request of his business travellers.
He told a press conference at the ITB in Berlin that business travellers made up 43% of the total travellers, by far the largest single group.
He said most were from the SME sector and many flew to destinations in Eastern Europe.
With the new service, passengers will be able to pay 5 to reserve their seat online any time in advance of their flight.
If they were to reserve the seat when they checked-in, there would be less choice but no charge.
Mr Winkelmann said Germanwings had already launched a "best-bargain" calendar which indicated the price of a ticket on any given day.
He said this had also been for the business traveller who often had to travel on set days but also wanted the best fare.
He said that Germanwings, which is part of the Lufthansa group, had an 82% load factor in 2007, the same as 2006. Profits for last year are also expected to be around the 8m figure of 2006.
Mr Winkelmann said the airline had dropped its service from Stuttgart to Paris CDG after the high speed rail servcie TGV Est opened last year, making the train journey faster than that by air.
He siad that for the same reason, it had not pursued plans to start services between Berlin and Hamburg and Cologne and Frankfurt.
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