Aircraft services group BBA Aviation said its performance since July 1 has been in line with expectations despite the difficult trading environment.It added signs of stabilisation have continued, with month-on-month flight activity improving. 'Whilst market conditions remain challenging, they have been more stable for the last four months,' said chief executive Simon Pryce.'The actions that we have taken to date have ensured that our business continues to operate robustly and this gives us confidence in our performance for the year.'