After a year at the helm Thomas Cook Chief Executive Harriet Green has steered the tour operator back to underlying third quarter profits and halved its debt mountain.Cook said the group had continued to make significant progress in transforming itself after the torrid time it had endured over the past few years. But she stressed: "This is just the start."The 172-year-old group swung to an underlying third quarter profit of £1m from losses of £23m last year. Margins improved by 110 basis points to 19.8% and net debt has more than halved to £452m at the end of June from £1.1bn at the same time last year.The company also reported encouraging current trading and said the recent political and social unrest in Egypt and Turkey had not had a significant impact. Summer bookings have been going well with about 85% of planned capacity now sold. Green has raised the group's total cost savings target for 2015 by £10m to £400m.Investec analyst James Hollins said: "Q3 EBIT was in line with our projections although strong summer trading leads us to believe that our full year 2013 estimates look prudent."Shares in Thomas Cook were up 2.9% at 158p at 09:20 on Thursday.TB