The group said it had enjoyed continuing high levels of passenger volume growth in its Southern and Southeastern train franchises, up 9.6 pct and 6.4 pct respectively in the quarter compared to the same three months last year, despite fare increases in January.

Go-Ahead said trading in its bus business had also been robust, although market conditions in its aviation services business Aviance remained difficult and would lead to lower full-year expectations for the division.

'In the light of this, together with a number of contractual delays and disappointments with new customers, management's expectations for the remainder of the year have been reduced,' it said.

Go-Ahead also said it had appointed Nick Swift as group finance director.

Swift, 42, will take up his role on July 17. Most recently, he worked as group finance manager at Hanson PLC (nyse: HAN - news - people ), where he was responsible for investor relations and had been head of tax and treasury and a group financial controller.